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38996 Publications

Tutorial: Thermal processes in short time annealing: application examples and current trends

Rebohle, L.

The tutorial gives an introduction to the technology of flash lamp annealing, discusses process-relevant issues like temperature profile, homogeneity and stress distribution, and presents a couple of examples in which thermal treatments of materials on short time scale is beneficial.

Keywords: flash lamp annealing; crystallization

Related publications

  • Invited lecture (Conferences)
    18th International Conference on Plasma Surface Engineering, 12.-15.09.2022, Erfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35401
Publ.-Id: 35401


177Lu(III) - and 225Ac(III) -labelled bispidine conjugates targeting neuroendocrine tumours

Kopp, I.; Kubeil, M.; Cieslik, P.; Brandt, F.; Zarschler, K.; Ullrich, M.; Pietzsch, J.; Bachmann, M.; Kopka, K.; Stephan, H.; Comba, P.

Bispidines (3,7-diazabicyclo[3.3.1]nonane) and their derivatives act as bifunctional
chelators (BFC), combining the advantages of multidentate macrocyclic and acyclic
ligands (e.g., high kinetic inertness, rapid radiolabelling under mild conditions) [1]. This
bicyclic chelator system shows a great diversity in terms of its denticity and type of
functional groups, yielding a wide range of multidentate ligands that can bind a variety of
different metal ions [1-3]. In addition, they allow a facile functionalisation of targeting
molecules such as peptides, peptidomimetics, and bispecific antibodies which can also
be used as target modules for adapter CAR T-cell cross-linkage [1, 4]. Herein, we present
a nonadentate bispidine ligand labelled with [177Lu]Lu3+ and [225Ac]Ac3+ at mild
conditions. The radiometal complexes have been obtained with high radiochemical yields
(99%) and are stable in human serum [3]. This is unique so far, as many chelators are
not able to bind both LuIII and AcIII under mild conditions (physiological pH, T<40°C) with
fast complexation kinetics and high molar activities (>100 MBq/nmol for [177Lu]Lu3+ and
~0.2 MBq/nmol for [225Ac]Ac3+). For targeting, the chelator was functionalised with a
peptidic somatostatin analogue (Tyr3
-octreotate), which addresses the somatostatin
subtype receptor 2 in neuroendocrine tumours. Both 177Lu(III)- and 225Ac(III)-labelled
conjugates were investigated towards their binding affinity and internalization in a murine
pheochromocytoma (MPC) and human pancreatic carcinoid (BON1) tumour cell line and
were compared with [177Lu]Lu(III)- and [
225Ac]Ac(III)-DOTA-TATE. The presented
177Lu(III)- and 225Ac(III)-labelled bispidine-conjugates show favourable labelling kinetics
and high radiostabilities in human serum. The radioconjugates exhibited dissociation
constants in the lower nanomolar range (<10 nM) and high internalisation rates (>95 %)
in both cell lines. In comparison to the corresponding DOTA-radioconjugates, milder
radiolabelling conditions might facilitate the labelling of heat-sensitive biomolecules.
Thus, this bispidine chelator shows promising characteristics for future nuclear medicine
applications.

References:

[1] P. Comba et al., Dalton Trans. 2018, 47, 9202. [2] L. Abad‐Galán et al., Chem. Eur.
J. 2021, 27, 10303. [3] P. Cieslik et al., Bispidine derivatives and the use thereof.
EP20216739, 2020. [4] G. Singh et al., Chem. Eur. J. 2020, 26, 1989.

Keywords: bispidine; neuroendocrine tumors; lutetium; actinium; CAR-T; bifunctional chelators; endoradiotherapy; chelator development; somatostatin

  • Lecture (Conference)
    Jahrestagung FG Nuklearchemie, 04.-06.10.2022, Bergisch Gladbach, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35400
Publ.-Id: 35400


Reduction of intrafraction pancreas motion using an abdominal corset compatible with proton therapy and MRI

Schneider, S.; Stefanowicz, S.; Jentsch, C.; Lohaus, F.; Thiele, J.; Haak, D.; Valentini, C.; Platzek, I.; Troost, E. G. C.; Hoffmann, A. L.

Background and Purpose:

Motion mitigation is of crucial importance in particle therapy (PT) of patients with abdominal tumors to ensure high-precision irradiation. Magnetic resonance imaging (MRI) is an excellent modality for target volume delineation and motion estimation of mobile soft-tissue tumors. Thus, the aims of this study were to develop an MRI- and PT-compatible abdominal compression device, to investigate its effect on pancreas motion reduction, and to evaluate patient tolerability and acceptance.
Materials and Methods:
In a prospective clinical study, 16 patients with abdominal tumors received an individualized polyethylene-based abdominal corset. Pancreas motion was analyzed using time- and phase resolved MRI scans (orthogonal 2D-cine and 4D MRI) with and without compression by the corset. The pancreas was manually segmented in each MRI data set and the population-averaged center-of-mass motion in inferior-superior (IS), anterior-posterior (AP) and left-right (LR) directions was determined. A questionnaire was developed to investigate the level of patient acceptance of the corset, which the patients completed after acquisition of the planning computed tomography (CT) and MRI scans.
Results:
The corset was found to reduce pancreas motion predominantly in IS direction by on average 47 % - 51 % as found in the 2D-cine and 4D MRI data, respectively, while motion in the AP and LR direction was not significantly reduced. Most patients reported no discomfort when wearing the corset.
Conclusion:
An MRI- and PT-compatible individualized abdominal corset was presented, which substantially reduced breathing-induced pancreas motion and can be safely applied with no additional discomfort for the patients. The corset has been successfully integrated into our in-house clinical workflow for PT of tumors of the upper abdomen.

Keywords: MR guided proton therapy; image guidance; tumor motion; abdominal compression

Permalink: https://www.hzdr.de/publications/Publ-35399
Publ.-Id: 35399


A brief summary about technetium: Origin, medical applications, and environmental immobilization strategies

Mayordomo, N.

This lecture will be given in the frame of the "Week science" at Universidad de Alcalá (Spain). I will give an overview about technetium origins, applications, and environmental remediation.

Keywords: Techenetium; Lecture; Environment; Applications

  • Invited lecture (Conferences) (Online presentation)
    Week of science at Universidad de Alcalá, 23.11.2022, Alcalá de Henares, Spain

Permalink: https://www.hzdr.de/publications/Publ-35397
Publ.-Id: 35397


177Lu-, 225Ac- and 111In-labelled nonadentate bispidine ligands synthesis, radiolabelling experiments and stability assays

Kopp, I.; Cieslik, P.; Kopka, K.; Bachmann, M.; Stephan, H.; Comba, P.; Kubeil, M.

Objectives
Bispidines (3,7-diazabicyclo[3.3.1]nonanes) are of great interest for the use in radiopharmaceutical applications. Combining the advantages of highly preorganised rigid macrocyclic ligands and the flexibility of open-chain ligands, they are able to form highly stable complexes at mild reaction conditions with a broad range of di- and trivalent metal ions.1,2 Here, we present a nonadentate bispidine ligand (Fig. 1) labelled with [177Lu]LuCl3, [225Ac]AcCl3 and [111In]InCl3 at mild conditions and report their stability and inertness in aqueous solution and human serum.3 The results in terms of radiolabelling conditions and serum stabilities are compared with the “gold standard” DOTA, which requires harsh radiolabelling conditions, and the octadentate bispidine ligand H2bispa.2,4

Methods
The bispidine ligand was synthesised according to literature on a multigram scale, with an overall yield of 5% over 9 steps.2

Radiolabelling experiments of the nonadentate bispidine ligand with [177Lu]Lu3+ and [225Ac]Ac3+ were carried out at 40 °C using 150 mM NH4OAc buffer (pH 6). Radiolabelling with [111In]In3+ was performed in the same buffer at room temperature. For comparison, the DOTA and the octadentate bispidine ligand H2bispa2 were labelled with the trivalent radiometals as well. The radiochemical yields and purities were monitored via radio-TLC and radio-HPLC for different ligand concentrations after 5 min, 30 min and 60 min. Radiostabilities in human serum were studied by radio-TLC and radio-SEC after 1 h, 1 d, 3 d and 7 d.

Results
Radiolabelling experiments gave quantitative yields for the formation of both 177Lu- and 225Ac‑complexes at 40 °C after 5 minutes for ligand concentrations of 10-6 mol/L. With [111In]In3+ a quantitative conversion was obtained even at room temperature after 60 minutes with a ligand concentration of 5·10-6 mol/L. For [177Lu]Lu3+, a molar activity of >100 MBq/nmol, for [225Ac]Ac3+ 0.2 MBq/nmol and for [111In]In3+ >20 MBq/nmol was found at the end of synthesis. Furthermore, the radiolabelled bispidine complexes showed high stability in human serum after 7 d ([225Ac]Ac‑bispidine: 80±2%; n=3, [177Lu]Lu-bispidine: 94%; n=2,), whereas only moderate stability was achieved for [111In]In-bispidine (74%; n=2 ) after 3 d.

Conclusions
The presented 177Lu- and 225Ac-labelled bispidine complexes showed favourable labelling kinetics and radiostabilities in human serum. The 111In-labelled bispidine gave moderate molar activities and stabilities in human serum. In comparison to DOTA, milder conditions for bispidine ligands allow the radiolabelling of heat-sensitive biomolecules.

References

[1] Comba, P.; Kerscher, M.; Rück, K.; Starke, M. Bispidines for Radiopharmaceuticals. Dalton Trans. 2018, 47, 9202–9220.

[2] Abad‐Galán, L.; Cieslik, P.; Comba, P.; Gast, M.; Maury, O.; Neupert, L.; Roux, A.; Wadepohl, H. Excited State Properties of Lanthanide(III) Complexes with a Nonadentate Bispidine Ligand. Chem. – Eur. J. 2021, 27, 10303–10312.

[3] Cieslik, P.; Kubeil, M.; Stephan, H.; Comba, P. Bispidine derivatives and the use thereof. EP20216739, 2020.

[4] Comba, P; Jermilova, U.; Orvig, C.; Patrick, B. O.; Ramogida, C.; Rueck, K.; Schneider, C.; Starke, M. Inorg. Chem. 2017, 23, 15945 – 15956.

Keywords: radiopharmacy; theranostics; bispidines; trivalent metals; actinium; lutetium; indium; ligand development

  • Lecture (Conference)
    Terachem, 14.-17.09.2022, Brixen, Italien

Permalink: https://www.hzdr.de/publications/Publ-35396
Publ.-Id: 35396


A novel bispidine-based chelator for radiopharmaceutical applications

Kubeil, M.; Ullrich, M.; Zarschler, K.; Pietzsch, J.; Kopka, K.; Bachmann, M.; Stephan, H.

Bispidines (3,7-diazabicyclo[3.3.1]nonane) and their derivatives act as bifunctional chelating agents (BFCAs). Combining the advantages of highly preorganised rigid macrocyclic ligands and the flexibility of open-chain ligands, bispidines are able to form highly stable complexes at mild reaction conditions with a broad range of di- and trivalent metal ions. Of particular interest, they allow the coupling to biological targeting vectors such as peptides, peptidomimetics, T cell receptor derivatives as well as any kind of natural and recombinant antibody derivatives to construct effective radiopharmaceuticals for diagnostic and therapeutic purposes. Here, we present a nonadentate bispidine ligand (Figure 1), which forms stable and inert complexes with [177Lu]LuCl3, [225Ac]AcCl3 and [111In]InCl3 at mild conditions. This is unique so far, as few chelators are able to tightly bind both Lu(III) and Ac(III) under mild conditions
(physiological pH, T<40°C) with fast complexation kinetics. We investigated the thermodynamic and kinetic properties of the radio-complexes. For targeting, the chelator was functionalised with a peptidic somatostatin analogue (Tyr3-octreotate, TATE), which addresses the somatostatin subtype receptor 2 in neuroendocrine tumors. The bispidine-TATE conjugate was labelled with 177Lu(III) and 225Ac(III) and investigated in SSTR2-positive mouse pheochromocytoma (MPC) and human pancreatic carcinoid tumour (BON-SSTR2) cell lines. Moreover, quantitative small animal SPECT imaging showed specific uptake of the [177Lu]Lu-conjugate in vivo in naturally SSTR2-positve MPC tumour allografts. Some structural optimisation will be required to further reduce off-target accumulation. However, the bispidine chelator shows a promising potential for a broad application in nuclear medicine, both in imaging and radionuclide therapy.

  • Lecture (Conference)
    Australian Society of Molecular Imaging (ASMI) 2022, 06.-07.10.2022, Melbourne, Australia

Permalink: https://www.hzdr.de/publications/Publ-35395
Publ.-Id: 35395


Towards personalized medicine: one chelator for imaging and therapy with lutetium-177 and actinium-225

Cieslik, P.; Kubeil, M.; Zarschler, K.; Ullrich, M.; Brandt, F.; Anger, K.; Wadepohl, H.; Kopka, K.; Bachmann, M.; Pietzsch, J.; Stephan, H.; Comba, P.

We report a nonadentate bispidine (3,7-diazabicyclo[3.3.1]nonane) that unveils the potential to bind theranostically relevant radionuclides, including indium-111, lutetium-177 and actinium-225 at mild labeling conditions. This radiopharmaceutical candidate allows the simultaneous application of imaging and treatment (radionuclide theranostics) without changing the type of bioconjugate, i.e. it allows the strong binding to an imaging and a therapeutic radionuclide by the same chelator. Since sophisticated coordination chemistry is required to achieve high thermodynamic and kinetic stability, it is not surprising that only a few chelators have been reported that are able to strongly bind several radionuclides to a satisfactory extent. Bispidine-derived ligands have proven to be ideal for di- and trivalent metal ions with generally fast complexation kinetics and high in vitro and in vivo stabilities. The presented (radio)complexes are formed under mild conditions (pH 6, <40°C) and exhibit thermodynamic stability and inertness in human serum comparable to the corresponding DOTA complexes. The bispidine-based complexing agent was conjugated to a peptide, targeting somatostatin type 2 receptors (SSTR2), overexpressed on neuroendocrine tumors. The 177Lu- and 225Ac-labeled conjugates were investigated, considering their binding to two different SSTR2 positive cell lines, including the human pancreatic carcinoid tumor (BON-SSTR2+) and the murine pheochromocytoma cell line (MPC). The biodistribution and accumulation pattern in MPC tumor-bearing mice was also evaluated. The LuIII and AcIII complexes studied show how ligand structures can be optimized in general by extending the denticity and varying the donor set in order to allow for fast complex formation and medically relevant inertness.

Keywords: bispidine; trivalent metal ions; radionuclide theranostics; somatostatin analogue; actinium; lutetium

  • Journal of the American Chemical Society 144(2022)47, 21555-21567
    Online First (2022) DOI: 10.1021/jacs.2c08438

Permalink: https://www.hzdr.de/publications/Publ-35394
Publ.-Id: 35394


Rare radioisotopes at the ready

Kvashnina, K.

The study of rare isotopes, including many in the f-block, is a key step to advancing our fundamental understanding of these elements but their scarcity poses challenges. Now, minute amounts of such materials have been isolated and characterized through complexation with polyoxometalate clusters.

Permalink: https://www.hzdr.de/publications/Publ-35393
Publ.-Id: 35393


Radiolabelling of nanoparticles for colloid tracing A versatile tool in nanosafety research

Schymura, S.; Mansel, A.; Kulenkampff, J.; Franke, K.

Many studies in the field of nanosafety research „do not offer any kind of clear statement on the safety of nanomaterials“, as methodological problems considerably hinder the reliable detection of nanoparticles (NPs) at the predicted low environmentally relevant concentrations.
The radiolabeling of nanoparticles has the potential for detecting nanoparticles at minimal concentrations in complex matrices, even against a same-element background, with unprecedented experimental ease, making it a versatile tool for NP release, transport, and uptake studies.

Keywords: Radiolabelling; Nanoparticles

  • Poster
    Week of Microbial Technologies, 07.-11.11.2022, Ljubljana, Slowenien

Permalink: https://www.hzdr.de/publications/Publ-35392
Publ.-Id: 35392


Ca-Caseinat-unterstützte Remineralisierung von Zähnen

Schymura, S.; Schneider, E.; Messerschmidt, J.; Lechner, B.-D.

Menschliche Zähne sind täglich chemischen Erosionsprozessen ausgesetzt, die zu einer Verschlechterung der Zahnsubstanz führen können. Verantwortlich hierfür sind in erster Line das Konsumieren von Säurehaltigen Getränken und Speisen. Niedriger pH, sowie Komplexierende Stoffe führen zu einer Demineralisierung des Zahn Hydroxylapatits {Ca5(PO4)3OH}2) (HAP). Es wird geschätzt dass weltweit 30-50% der Milchzähne und 20-45% der permanenten Zähne von Zahnerosion betroffen sind. Folgen von Zahnerosion können ein erhöhtes Kariesrisiko, Zahnsensibilität, Zahnverfärbung und im schlimmsten Fall Zahnverlust sein.
Eine potentielle Maßnahme um Zahnerosion entgegenzuwirken stellt die Förderung der Remineralisierung dar, indem die Calcium und Phosphat-Konzentration im Speichel erhöht wird, z. B. durch die Gabe von Casein, einem Milchprotein. Die im Casein enthaltenen Ca9(PO4)6 Nanocluster können in die erodierte Zahnsubstanz eingebaut werden und die Schäden rückgängig machen. Unter Verwendung der Weißlichtinterferometrie zur Rauheitsanalyse zeigen wir die Dynamik der DEM/REM Prozesse in-Vitro und zeigen in Fallstudien die Anwendung von Ca Kaseinat als wenig intrusive Behandlungsmethode mit REM Potential in-Vivo.

Keywords: Zahnremineralisation; Apatit; Ca-Caseinat

  • Poster
    15. Thüringer Zahnärztetag, 25.-26.11.2022, Erfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35391
Publ.-Id: 35391


Ca-Caseinate-enhanced remineralisation of dental apatite

Schymura, S.; Schneider, E.; Messerschmidt, J.; Lechner, B.-D.

Human teeth are subject to chemical erosion processes that can lead to a loss of tooth hard substance. Low pH and complexing agents in food and drink can demineralize the dental hydroxyapatite. It is estimated that 20-45 % of permant teeth worldwide are affected by tooth errosion. This can lead to increased caries risk, tooth sensitivity, tooth colouration and in the worst case tooth loss. One potential treatment of tooth errosion is the promotion of naturally ocurring remineralisation processes, e.g. by application of caseine milk protein. The Ca9(PO4)6 nanoclusters have the potential to cure damaged tooth material. Using vertical scanning interferometry we show the dynamics of de- and remineralisation tooth samples by analysis of the surface roughness development.

Keywords: Remineralisation; apatite; dental material; Ca-Caseinate

  • Invited lecture (Conferences)
    Week of Microbial Technologies, 07.-11.11.2022, Ljubljana, Slowenien

Permalink: https://www.hzdr.de/publications/Publ-35390
Publ.-Id: 35390


Molecular Structures of the Silicon Pyridine-2-(thi)olates Me3Si(pyX), Me2Si(pyX)2 and Ph2Si(pyX)2 (py = 2-Pyridyl, X = O, S), and Their Intra- and Intermolecular Ligand Exchange in Solution

Seidel, A.; Weigel, M.; Ehrlich, L.; Gericke, R.; Brendler, E.; Wagler, J.

A series of pyridine-2-olates (pyO) and pyridine-2-thiolates (pyS) of silicon was studied in solid state and in solution. The crystal structures of Me3Si(pyO) (1a), Me3Si(pyS) (1b), Me2Si(pyO)2 (2a), Me2Si(pyS)2 (2b), Ph2Si(pyO)2 (3a) and Ph2Si(pyS)2 (3b) were determined by X-ray diffraction. For that purpose, crystals of the (at room temperature) liquid compounds 1a and 1b were grown in a capillary on the diffractometer. Compounds 1a, 1b, 2a, 2b and 3a feature tetracoordinate silicon atoms in the solid state, whereas 3b gave rise to a series of four crystal structures in which the Si atoms of this compound are hexacoordinate. Two isomers (3b1 with all-cis arrangement of the C2N2S2 donor atoms in P-1, and 3b2 with trans S-Si-S axis in P21/n) formed individual crystal batches, which allowed for their individual 29Si NMR spectroscopic study in the solid state (the determination of their chemical shift anisotropy tensors). Furthermore, the structures of a less stable modification of 3b2 (in C2/c) as well as a toluene solvate 3b2 (toluene) (in P-1) were determined. In CDCl3, the equimolar solutions of the corresponding pairs of pyO and pyS compounds (2a/2b and 3a/3b) showed substituent scrambling with the formation of the products Me2Si(pyO)(pyS) (2c) and Ph2Si(pyO)(pyS) (3c), respectively, as minor components in the respective substituent exchange equilibrium.

Keywords: chemical shift anisotropy; 2-hydroxypyridine; hypercoordination; 2-mercaptopyridine; organosilanes; quantum chemical calculation

Permalink: https://www.hzdr.de/publications/Publ-35387
Publ.-Id: 35387


Bonding Trends in Tetravalent Actinide (Th - Pu) Complex Series

Gericke, R.; März, J.; Kaden, P.; Patzschke, M.; Radoske, T.; Fichter, S.; Blei, M. K.; Schmidt, M.; Stumpf, T.

Actinides play an important role in chemical engineering and environmental science related to the nuclear industry or nuclear waste repositories.1 One of the major tools to obtain a profound knowledge about actinide (An) binding is their coordination chemistry. However, the understanding of complexation properties of the actinides is lacking behind those of the d- or 4f-elements. Characteristic of the actinides is their huge variety of possible oxidation states, typically ranging from +II to +VII for early An. A suitable approach to explore fundamental physico-chemical properties of the actinides is to study series of isostructural An compounds in which the An is in the same oxidation state.2 Therefore our investigations are directed towards the synthesis of actinide complexes with the f-element in the oxidation state IV, the dominant oxidation state particularly under anoxic environmental conditions. Observed changes in e.g., the binding situation or magnetic effects along such a series may deliver insight into the elements’ unique electronic properties mainly originating from the f-electrons. One important question in the field of An chemistry is the degree of “covalency” in compounds across the An series,3 which may be addressed by systematic studies on series of An compounds, including transuranium (TRU) elements.
In these studies, we investigate the coordination chemistry of tetravalent actinides (An(IV)), using organic mono- or dianionic ligands with O- and mixed O/N-donor atoms of the acetylacetonate and salen-type.4 The An complexes are typically synthesized via salt metathesis reactions under strict exclusion of moisture and air. Single crystal X-ray diffraction analysis provides insight into isostructural complex series, which were achieved in each case. The resulting compounds were further analysed by NMR, IR, UV-vis-NIR, and EPR spectroscopy and cyclic voltammetry. These results are used as a basis to further analyse bonding trends along the actinide series by means of quantum chemical calculations.
From the results, trendlines along the actinides An = Th, U, Np and Pu in various complex series were obtained, which shed some light in the ongoing debate of covalency in actinide bonding.

References
[1] L. S. Natrajan, A. N. Swineburn, M. B. Andrews, S. Randall, S. L. Heath, Coord. Chem. Rev. 2014, 266-267, 171-193.
[2] M. B. Jones, A. J. Gaunt, J. C. Gordon, N. Kaltsoyannis, Chem. Sci. 2013, 4, 1189-1203.
[3] M. P. Kelley, J. Su, M. Urban, M. Luckey, E. R. Batista, P. Yang, J. C. Shafer, J. Am. Chem. Soc. 2017, 139, 9901-9908.
[4] T. Radoske, J. März, M. Patzschke, P. Kaden, O. Walter, M. Schmidt, T. Stumpf, Chem. Eur. J. 2020, 26, 16853-16859.

Acknowledgement
This study was supported by the German Federal Ministry of Education and Research (BMBF) funding under the project No. 02NUK046B (FENABIUM).

Keywords: actinides; NMR; EPR; single crystal X-ray diffaction; quantum chemical calculations

Related publications

  • Invited lecture (Conferences)
    Terrae Rarae - Tage der Seltenen Erden, 27.-29.09.2022, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-35386
Publ.-Id: 35386


[An(acac)4] - complexes revisited

Gericke, R.; Kaden, P.

Actinides (An) play an important role in chemical research and environmental science related to the nuclear industry or nuclear waste repositories.1 Investigating their coordination chemistry can function as a tool to obtain fundamental understanding of actinide binding. Due to the radiotoxicity of actinide complexes, special care in handling those material need to be employed in form of working in a controlled area lab. Therefore, the understanding of complexation properties of the actinides, in particular the transuranium (TRU) elements, is lacking behind those of the d- or 4f-elements, which can be handeled in ordinary laboratories.
For the early actinides possible oxidation states are typically ranging from +II to +VII. A suitable approach to explore fundamental physico-chemical properties of the actinides is to study series of isostructural An compounds in which the An is in the same oxidation state.2 Therefore our investigations are directed towards the synthesis of actinide complexes (An = Th, U, Np and Pu) with the f-element in the oxidation state IV, the dominant oxidation state particularly under anoxic environmental conditions. Observed changes in e.g., the binding situation or magnetic effects along such a series deliver insight into the elements’ unique electronic properties mainly originating from the f-electrons. One important question in the field of An chemistry is the degree of “covalency” in compounds across the An series,3 which may be addressed by systematic studies on series of An compounds, including transuranium (TRU) elements.
An-complexes using pure O-donor ligand systems can act as molecular mimic for related An-O-systems, e.g. UO2 used as fuel in nuclear reactors. In these studies, we investigate the coordination chemistry of tetravalent actinides (An(IV)), using an organic monoanionic ligand with O-donor atoms of the acetylacetonate (acac) type. Since 1958, actinide complexes of the type [An(acac)4] have structurally been caracterized at ambient temperature.4-8 However, spectroscopic data is limited to vibrational spectroscopy especially for the transuranium complexes, leaving open questions of the actinide bonding. The [An(acac)4] complexes are typically synthesized via salt metathesis reactions under strict exclusion of moisture and air. Single crystal X-ray diffraction analysis at 100 K provides insight into isostructural complex series, which were achieved in each case. In order to obtain further insight into the electronic structure of these complexes, the compounds were further analysed by NMR, IR, UV-vis-NIR, and EPR spectroscopy. The redox chemistry of the series of [An(acac)4] complexes in NCMe was further investigated with cyclic voltammetry. These results are used as a basis to further analyse bonding trends along the actinide series by means of quantum chemical calculations.
From the results, trendlines along the actinides An = Th, U, Np and Pu in this complex series were obtained, which shed some light in the ongoing debate of covalency in actinide bonding.

References
1. L. S. Natrajan, A. N. Swineburn, M. B. Andrews, S. Randall, S. L. Heath, Coord. Chem. Rev. 2014, 266-267, 171-193.
2. M. B. Jones, A. J. Gaunt, J. C. Gordon, N. Kaltsoyannis, Chem. Sci. 2013, 4, 1189-1203.
3. M. P. Kelley, J. Su, M. Urban, M. Luckey, E. R. Batista, P. Yang, J. C. Shafer, J. Am. Chem. Soc. 2017, 139, 9901-9908.
4. D. Grdenić, B. Matković, Nature 1958, 182, 465-466.
5. D. Grdenić, B. Matković, Acta Cryst. 1959, 12, 817-817.
6. B. Allard, Acta Chem. Scand. 1972, 26, 3492-3504.
7. D. Brown, B. Whittaker, J. Tacon, J. Chem. Soc., Dalton Trans. 1975, 1, 34-39.
8. B. Allard, J. Inorg. Nucl. Chem. 1976, 38, 2109-2115.

Keywords: actinides; NMR; EPR; single crystal X-ray diffraction; quantum chemical calculations

  • Lecture (Conference)
    Actinides revisited 2022, 21.-23.09.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-35385
Publ.-Id: 35385


Intelligent Materials and Systems

Makarov, D.

In this presentation, we review current research activities at the FWID.

Keywords: curvature effects in magnetism; antiferromagnetic spintronics; magnetic soft robots

Related publications

  • Lecture (others)
    seminar at the Central European Institute of Technology (CEITEC), 03.11.2022, Brno, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-35384
Publ.-Id: 35384


Learning-based systems for assessing hazard places of contagious diseases and diagnosing patient possibility

Davoodi Monfared, M.; Ghaffari, M.

To manage the propagation of infectious diseases, particularly fast-spreading pandemics, it is necessary to provide information about possible infected places and individuals, however, it needs diagnostic tests and is time-consuming and expensive. To smooth these issues, and motivated by the current Coronavirus disease (COVID-19) pandemic, in this paper, we propose a learning-based system and a hidden Markov model (i) to assess hazardous places of a contagious disease, and (ii) to predict the probability of individuals’ infection. To this end, we track the trajectories of individuals in an environment. For evaluating the models and the approaches, we use the Covid-19 outbreak in an urban environment as a case study. Individuals in a closed population are explicitly represented by their movement trajectories over a period of time. The simulation results demonstrate that by adjusting the communicable disease parameters, the detector system and the predictor system are able to correctly assess the hazardous places and determine the infection possibility of individuals and cluster them accurately with high probability, i.e., on average more than 96%. In general, the proposed approaches to assessing hazardous places and predicting the infection possibility of individuals can be applied to contagious diseases by tailoring them to the influential features of the disease.

Keywords: Machine learning; Trajectory tracking; Patient prediction; Hidden Markov model; Covid-19; Trajectory clustering

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  • Secondary publication expected from 18.10.2023

Permalink: https://www.hzdr.de/publications/Publ-35381
Publ.-Id: 35381


Superconductivity in the amorphous phase of the half-Heusler TiNiSn alloy

Barzola-Quiquia, J.; Osmic, E.; Bercoff, P. G.; Venosta, L.; Häussler, P.

Amorphous TiNiSn films were prepared at 𝑇 ≈ 4.2 K and resistance 𝑅(𝑇 ) and thermopower 𝑆(𝑇 ) have been investigated. 𝑅(𝑇 ) shows that the sample is superconducting and the transition temperature 𝑇𝑐 increases with increasing annealing temperature, being the maximum 𝑇𝑐3 = 4.19 K. The electron–phonon coupling estimated from 𝑆(𝑇 ) results is very close to the value calculated using McMillan equation for the superconducting transition 𝑇𝑐 , indicating that amorphous TiNiSn is an intermediate electron–phonon coupled superconductor. After annealing up to 𝑇 = 850 K, the amorphous sample crystallizes at 𝑇𝐾 ≈ 785 K. The atomic structure and high stability of the amorphous phase can be explained in the framework of electronically stabilized Hume–Rothery phases, where hybridization from Ti-𝑑 and Ni-𝑑 electrons plays an important role. The crystallized sample shows a well-ordered half-Heusler crystalline phase, space group 𝐹43𝑚, with a TiNiSn atomic order in the unit cell instead of the common NiTiSn type.

Permalink: https://www.hzdr.de/publications/Publ-35376
Publ.-Id: 35376


Dimensional reduction and incommensurate dynamic correlations in the S = 1/2 triangularlattice antiferromagnet Ca3ReO5Cl2

Zvyagin, S. A.; Ponomaryov, A. N.; Wosnitza, J.; Hirai, D.; Hiroi, Z.; Gen, M.; Kohama, Y.; Matsuo, A.; Matsuda, Y. H.; Kindo, K.

The observation of spinon excitations in the S = 1/2 triangular antiferromagnet Ca3ReO5Cl2 reveals a quasi-one-dimensional (1D) nature of magnetic correlations, in spite of the nominally 2D magnetic structure. This phenomenon is known as frustration-induced dimensional reduction. Here, we present high-field electron spin resonance spectroscopy and magnetization studies of Ca3ReO5Cl2, allowing us not only to refine spin-Hamiltonian parameters, but also to investigate peculiarities of its low-energy spin dynamics. We argue that the presence of the uniform Dzyaloshinskii-Moriya interaction (DMI) shifts the spinon continuum in momentum space and, as a result, opens a zero-field gap at the Γ point.We observed this gap directly. The shift is found to be consistent with the structural modulation in the ordered state, suggesting this material as a perfectmodel triangular-lattice ystem,where a pure DMI-spiral ground state can be realized.

Permalink: https://www.hzdr.de/publications/Publ-35375
Publ.-Id: 35375


Direct numerical simulation of particles, rigid and flexible fibers interacting with a drop

Lecrivain, G.; Hampel, U.; Yamamoto, R.; Taniguchi, T.

The present work results from a three-year collaboration between the Helmholtz-Zentrum Dresden-Rossendorf (Germany) and the University of Kyoto (Japan), which took place within the frame of International Marie Curie Fellowship. The dynamics of colloidal particles and fibers at a fluidic interface is of significant importance in various processes, one of which is the flotation process. It is widely used in the mineral industry for the selective separation of particles based on their affinity to rising gas bubbles. It is also one of the most common de-inking processes used to recover the paper fibers. In an attempt to develop numerical tools, which will find future applications in the flotation process, direct numerical simulations of particles, rigid and flexible fibers interacting with a drop were performed.

Keywords: Flotation; Fibers; Three phase flow

  • Lecture (Conference)
    4th International Symposium on Multiscale Multiphase Process Engineering (MMPE), 25.-28.09.2022, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-35373
Publ.-Id: 35373


A phase-field model to simulate foams flowing in an obstructed channel

Lecrivain, G.; Heitkam, S.; Hampel, U.

Numerical simulations are a valid alternative for the investigation of flowing foams in two- and three-dimensional domains. Large advances in this field have for instance been achieved with the Surface Evolver [Brakke, 1992; Cox, 2006], which discretizes the air-liquid interfaces of the foam with a triangle mesh. A numerical model derived from the phase field theory is here suggested to simulate flowing foams with gas concentration (ε) ranging from 40 to 99%.

Keywords: Foam; Phase field model

  • Poster
    EUFOAM 2022, 03.-06.07.2022, Kraków, Poland

Permalink: https://www.hzdr.de/publications/Publ-35372
Publ.-Id: 35372


Covalent Organic Framework Thin-film Photodetectors from Solution Processable Porous Nanospheres

Bag, S.; Sekhar Sasmal, H.; Pratap Chaudhary, S.; Dey, K.; Blätte, D.; Guntermann, R.; Zhang, Y.; Položij, M.; Kuc, A. B.; Shelke, A.; Vijayaraghavan, R. K.; Ajithkumar, T. G.; Bhattacharyya, S.; Heine, T.; Bein, T.; Banerjee, R.

The synthesis of homogeneous covalent organic framework (COF) thin films on the desired substrate with decent crystallinity, porosity, and uniform thickness has great potential for optoelectronic applications. We have used a solution- processable sphere transmutation process to synthesize 300±20 nm uniform COF thin films on a 2×2 cm2 TiO2-coated FTO surface. This process controls the nucleation of COF crystallites and molecular morphology that helps the nanospheres to arrange periodically to form homogeneous COF thin films. We have synthesized four COF thin films (TpDPP, TpEtBt, TpTab, and TpTta) with different functional backbones. In a close agreement between the experiment and density functional theory, the TpEtBr COF film showed the lowest optical bandgap (2.26 eV) and highest excited-state lifetime (8.52 ns) among all four COF films. Hence, the TpEtBr COF film can participate in efficient charge generation and separation. We constructed optoelectronic devices having a glass/FTO/TiO2/COF-film/Au architecture, which serves as a model system to study the optoelectronic charge transport properties of COF thin films under dark and illuminated conditions. The visible light with a calibrated intensity of 100 mW cm-2 was used for the excitation of COF thin films. All the COF thin films exhibit significant photocurrent after illumination with visible light in comparison to the dark. Hence, all the COF films behave as good photoactive substrates with minimal pin hole defects. The fabricated out-of-plane photodetector device based on the TpEtBr COF thin film exhibits high photocurrent density (2.65 ± 0.24 mA cm-2 at 0.5 V) and hole mobility (8.15±0.64 ×10-3 cm2 V-1 S- 1) compared to other as-synthesized films, indicating the best photoactive characteristics.

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  • Secondary publication expected from 09.01.2024

Permalink: https://www.hzdr.de/publications/Publ-35371
Publ.-Id: 35371


Software publication: Structure-imposed electronic topology in cove-edged graphene nanoribbons

Arnold, F. M.; Liu, T.-J.; Kuc, A. B.; Heine, T.

The repository contains the inputs and outputs of tight-binding (TB) calculations of ZGNR-C based on PythTB. For each analysed structure one subdirectory is created, labelled as "N-ZGNR-C_a_b_inv_cellα_termination". This corresponds to a N-ZGNR-C(a,b) with inversion center at the unit cell boundary S or L ("inv"), unit cell angle α
("cellα": 60°, 90°, or 120°) and a given unit cell termination (armchair, zigzag or bearded). Each directory contains the atomic structure in xsf and cif format, the PythTB input file, the output as a json file, and the calculated band structure as image file. The json file contains the band structure information (path and eigenvalues), the raw Zak phase in units of π without modulo 2, and the final ℤ2 invariant.

Related publications

  • Software in external data repository
    Publication year 2022
    Programming language: python
    System requirements: linux
    License: Creative Commons Attribution 4.0 International
    Hosted on ZENODO: Link to location
    DOI: 10.5281/zenodo.7254202

Permalink: https://www.hzdr.de/publications/Publ-35370
Publ.-Id: 35370


New Perspectives for Warm Dense Matter Theory: from Quantum Monte Carlo to Temperature Diagnostics

Dornheim, T.

Warm dense matter (WDM)---an extreme state that is characterized by extreme densities and temperatures---has emerged as one of the most active frontiers in plasma physics and material science. In nature, WDM occurs in astrophysical objects such as giant planet interiors and brown dwarfs. In addition, WDM is highly important for cutting-edge technological applications such as inertial confinement fusion and the discovery of novel materials.
In the laboratory, WDM is studied experimentally in large facilities around the globe, and new techniques have facilitated unprecedented insights into exciting phenomena like the formation of nanodiamonds at planetary interior conditions [1]. Yet, the interpretation of these experiments requires a reliable diagnostics based on accurate theoretical modeling, which is a notoriously difficult task [2].
In this talk, I give an overview of recent developments in this field [3,4], which will allow for the first time to rigorously treat the intricate interplay of Coulomb coupling with thermal excitations and quantum degeneracy effects. Moreover, I show how quantum Monte Carlo simulation techniques will help to decisively improve density functional theory (DFT) simulations of WDM, thereby opening up new perspectives, such as the experimental and theoretical study of nonlinear effects [5,6]. Finally, I will present a new idea to extract the exact temperature from an X-ray Thomson scattering experiment without any models or simulations [7].

[1] D. Kraus et al., Nature Astronomy 1, 606-611 (2017)
[2] M. Bonitz et al., Physics of Plasmas 27, 042710 (2020)
[3] T. Dornheim et al., Physics Reports 744, 1-86 (2018)
[4] T. Dornheim et al., Physical Review Letters 121, 255001 (2018)
[5] T. Dornheim et al., Physical Review Letters 125, 085001 (2020)
[6] Zh. Moldabekov et al., Journal of Chemical Theory and Computation 18, 2900-2912 (2022)
[7] T. Dornheim et al., arXiv:2206.12805

  • Lecture (others)
    HEDS Seminar Series, 27.10.2022, Livermore, California, USA

Permalink: https://www.hzdr.de/publications/Publ-35361
Publ.-Id: 35361


New Perspectives for the ab-initio Simulation and Diagnostics of Warm-dense Matter

Dornheim, T.

Warm dense matter (WDM)---an extreme state that is characterized by extreme densities and temperatures---has emerged as one of the most active frontiers in plasma physics and material science. In nature, WDM occurs in astrophysical objects such as giant planet interiors and brown dwarfs. In addition, WDM is highly important for cutting-edge technological applications such as inertial confinement fusion and the discovery of novel materials.
In the laboratory, WDM is studied experimentally in large facilities around the globe, and new techniques have facilitated unprecedented insights into exciting phenomena like the formation of nanodiamonds at planetary interior conditions [1]. Yet, the interpretation of these experiments requires a reliable diagnostics based on accurate theoretical modeling, which is a notoriously difficult task [2].
In this talk, I give an overview of recent developments in this field [3,4], which will allow for the first time to rigorously treat the intricate interplay of Coulomb coupling with thermal excitations and quantum degeneracy effects. Moreover, I show how quantum Monte Carlo simulation techniques will help to decisively improve density functional theory (DFT) simulations of WDM, thereby opening up new perspectives, such as the experimental and theoretical study of nonlinear effects [5,6]. Finally, I will present a new idea to extract the exact temperature from an X-ray Thomson scattering experiment without any models or simulations [7].

[1] D. Kraus et al., Nature Astronomy 1, 606-611 (2017)
[2] M. Bonitz et al., Physics of Plasmas 27, 042710 (2020)
[3] T. Dornheim et al., Physics Reports 744, 1-86 (2018)
[4] T. Dornheim et al., Physical Review Letters 121, 255001 (2018)
[5] T. Dornheim et al., Physical Review Letters 125, 085001 (2020)
[6] Zh. Moldabekov et al., Journal of Chemical Theory and Computation 18, 2900-2912 (2022)
[7] T. Dornheim et al., arXiv:2206.12805

  • Invited lecture (Conferences)
    APS DPP Meeting, 17.10.2022, Spokane, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-35360
Publ.-Id: 35360


Our Competences to support Design for Sustainability

van den Boogaart, K. G.; Parvez, A. M.

The presentation provides a detailed information on our competences and approaches for design for sustainability and design for recycling for cooperation with the industry for that topic: Quantification of impacts along the whole product cycle, the 9R principle, qualitative and quantitative information, the design support cycle, the product cycle and key properties of properly designed products including material decomposability, behaviour in destructuring, chemical properties, and route choices.

Keywords: Design for Recyclability; Design for Sustainability; LCA; Process Modelling

  • Lecture (others) (Online presentation)
    Kooperationstreffen mit Continental, 02.11.2022, Freiberg, Deutschland
  • Lecture (others) (Online presentation)
    Kooperationstreffen mit Draeger, 22.11.2022, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35359
Publ.-Id: 35359


Data publication: Coherent coupling of metamaterial resonators with dipole transitions of boron acceptors in Si

Meng, F.; Han, F.; Kentsch, U.; Pashkin, O.; Fowley, C.; Rebohle, L.; Thomson, M. D.; Suzuki, S.; Asada, M.; Roskos, H. G.

FTIR transmission spectra of the samples at various temperatures

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Permalink: https://www.hzdr.de/publications/Publ-35358
Publ.-Id: 35358


Current state and Guidance on Arterial Spin Labeling Perfusion MRI in Clinical Neuroimaging

Lindner, T.; Bolar, D. S.; Achten, E.; Barkhof, F.; Bastos-Leite, A. J.; Detre, J. A.; Golay, X.; Günther, M.; Wang, D. J.; Haller, S.; Ingala, S.; Jäger, H. R.; Jahng, G.-H.; Juttukonda, M. R.; Keil, V. C.; Kimura, H.; Ho, M.-L.; Lequin, M.; Lou, X.; Petr, J.; Pinter, N.; Pizzini, F. B.; Smits, M.; Sokolska, M.; Zaharchuk, G.; Mutsaerts, H. J.

This review article focuses on clinical applications of arterial spin labeling (ASL) and is part of a wider effort from the International Society for Magnetic Resonance in Medicine (ISMRM) Perfusion Study Group to update and expand on the recommendations provided in the 2015 the consensus paper on ASL. While the 2015 consensus paper provided general guidelines for clinical applications of ASL MRI, there was a lack of guidance on disease-specific parameters. Since that time, the clinical availability and o clinical demand for ASL MRI has increased. This position paper provides guidance on using ASL in specific clinical scenarios, including acute ischemic stroke and steno-occlusive disease, arteriovenous malformations and fistulas, tumors, neurodegenerative disease, pediatric applications, and seizures/epilepsy, focusing on disease-specific considerations for sequence optimization and interpretation. We present several neuroradiological applications where ASL can provide unique diagnostic information. This guidance is intended for anyone interested in using ASL in a routine clinical setting — i.e., on a single-subject basis rather than in cohort studies — building on the previous ASL consensus review.

Permalink: https://www.hzdr.de/publications/Publ-35356
Publ.-Id: 35356


Data publication: Magnetic induction processes in hot Jupiters, application to KELT-9b

Dietrich, W.; Kumar, S.; Poser, A. J.; French, M.; Nettelmann, N.; Redmer, R.; Wicht, J.

This dataset contains ionization and transport values for ultra-hot Jupiter KELT-9b. The transport coefficients are used in the calculation of the atmospheric magnetic field of the planet.

Keywords: magnetic fields; plasmas; exoplanet; atmospheres – planets and satellites

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Permalink: https://www.hzdr.de/publications/Publ-35355
Publ.-Id: 35355


Coherent coupling of metamaterial resonators with dipole transitions of boron acceptors in Si

Meng, F.; Han, F.; Kentsch, U.; Pashkin, O.; Fowley, C.; Rebohle, L.; Thomson, M. D.; Suzuki, S.; Asada, M.; Roskos, H. G.

We investigate the coherent coupling of metamaterial resonators with hydrogen-like boron acceptors in Si at cryogenic temperatures. When the resonance frequency of the metamaterial, chosen to be in the range 7–9 THz, superimposes the transition frequency from the ground state of the acceptor to an excited state, Rabi splitting as large as 0.4 THz is observed. The coherent coupling shows a feature of cooperative interaction, where the Rabi splitting is proportional to the square root of the density of the acceptors. Our experiments may help to open a possible route for the investigation of quantum information processes employing strong coupling of dopants in cavities.

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  • Secondary publication expected from 20.09.2023

Permalink: https://www.hzdr.de/publications/Publ-35354
Publ.-Id: 35354


Physics-Informed Neural Networks as Solvers for the Time-Dependent Schrödinger Equation

Shah, K.; Stiller, P.; Hoffmann, N.; Cangi, A.

We demonstrate the utility of physics-informed neural networks (PINNs) as solvers for the non-relativistic, time-dependent Schrödinger equation. We study the performance and generalisability of PINN solvers on the time evolution of a quantum harmonic oscillator across varying system parameters, domains, and energy states.

Keywords: physics-informed neural networks; machine learning; Schrödinger equation

Permalink: https://www.hzdr.de/publications/Publ-35353
Publ.-Id: 35353


Learning the Schrödinger Equation

Shah, K.

We present an educational module incorporating machine learning into physics curriculum, which can be used can be used for a Quantum Mechanics course. The module will begin with introduction to the time dependent Schrödinger Equation including a tutorial on analytical solutions for the Quantum Harmonic Oscillator. The second portion of this module will consist of a solution of this system using neural networks. Students are encouraged to try different parameters and modify the code to fit other systems.

Keywords: data science; machine learning; physics education

  • Invited lecture (Conferences)
    DSECOP 2022 Data Science in Physics Workshop, 22.06.2022, College Park, Maryland, USA
  • Software in external data repository
    Publication year 2022
    Programming language: Python
    System requirements: Python
    License: MIT License
    Hosted on GitHub: Link to location

Permalink: https://www.hzdr.de/publications/Publ-35352
Publ.-Id: 35352


Flotation separation of galena from sphalerite using hyaluronic acid (HA) as an environmental-friendly sphalerite depressant

Zhu, H.; Yang, B.; Rudolph, M.; Zhang, H.; He, D.; Luo, H.

A disaccharide unit glycosaminoglycan named hyaluronic acid (HA) was exploited as a novel sphalerite depressant in the flotation separation of Pb-Zn sulfides in this study. The effect of HA on the flotation of galena and sphalerite were evaluated by micro-flotation tests. The depression mechanisms were investigated by adsorption capacity, Zeta potential and X-ray photoelectron spectroscopy (XPS) analysis. The results of microflotation tests proved that HA was an efficient and selective sphalerite depressant, which could depress sphalerite but hardly influence the flotation of galena to achieve desirable separation results using sodium isobutyl xanthate as collector. The results of adsorption capacity and Zeta potential tests suggested that HA was more inclined to adsorb on sphalerite surface than that of galena, which hindered the adsorption of SIBX on sphalerite surface but insignificantly affected the interaction of SIBX with galena surface. XPS results indicated that HA chemisorbed on sphalerite through the coordination of carboxyl and N-acetyl groups with Zn sites, whereas it physically adsorbed on galena surface by means of hydrophobic interaction.

Keywords: Sphalerite; Galena; Hyaluronic acid; Depressant; Flotation separation

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  • Secondary publication expected from 12.08.2023

Permalink: https://www.hzdr.de/publications/Publ-35351
Publ.-Id: 35351


Physics-Informed Neural Networks for Quantum Dynamics of Electrons

Shah, K.; Cangi, A.

We demonstrate the utility of Physics Informed Neural Network based solvers for the solution of Time-Dependent Schrödinger Equation. We study the performance and generalisability of PINN solvers on a simple quantum system. The method developed here can be potentially extended as a surrogate model for the Time-Dependent Density Functional Theory workflow, enabling the simulation of large-scale calculations of electron dynamics in matter exposed to strong electromagnetic fields, high temperatures and pressures.

  • Poster
    Helmholtz AI Conference, 02.06.2022, Dresden, Germany
  • Lecture (Conference)
    Multiscale Modeling of Matter under Extreme Conditions, 15.09.2022, Görlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-35350
Publ.-Id: 35350


Physics Informed Neural Networks based Solvers for the Time-Dependent Schrödinger Equation

Shah, K.; Cangi, A.

We demonstrate the utility of Physics Informed Neural Network based solvers for the solution of the Time-Dependent Schrödinger Equation. We study the performance and generalisability of PINN solvers on a simple quantum system. The method developed here can be potentially extended as a surrogate model for Time-Dependent Density Functional Theory, enabling the simulation of large-scale calculations of electron dynamics in matter exposed to strong electromagnetic fields, high temperatures, and pressures.

Keywords: time-dependent density functional theory; physics informed neural networks

  • Poster
    DFT Methods for Matter under Extreme Conditions, 21.02.2022, Görlitz, Germany
  • Poster
    Strongly Coupled Coulomb Systems, 25.07.2022, Görlitz, Germany
  • Poster
    Big data analytical methods for complex systems, 06.10.2022, Wrocław, Poland
  • Poster
    HZDR DocSeminar, 20.10.2022, Wrocław, Poland

Permalink: https://www.hzdr.de/publications/Publ-35349
Publ.-Id: 35349


Ultrasound imaging of liquid fraction in foam

Emmerich, H.; Knüpfer, L.; Heitkam, S.; Starke, E.; Trtik, P.; Schaller, L.; Weik, D.; Czarske, J.

Flotation is an important process in liquid-solid and solid-solid separation, whereby desired solids in suspensions are recovered by their attachment to gas bubbles. Monitoring the process is essential for increased grade of quality and reduced water consumption. However, in situ measurements of the froth’s phases (liquid, air, particles) or volume flow, which is easily integrable in industrial process are not available. In this paper, we propose an instrumentation with ultrasound transducers of center frequency of 135 kHz and electrodes to measure the liquid fraction distribution in foam and froth with high spatio-temporal resolution of 6.65 mm (axial), 13 mm (lateral) and 1 Hz. The measurement system was calibrated in homogeneous, steady foam by an integral conductivity measurement. A backscatter model was applied to reduce the effect of ultrasound shadowing and enhance quantitative liquid fraction estimates. The measurement was validated by neutron radiography. An averaged absolute and relative measurement uncertainty of 0.17 ·10 −2 and 35.1 % for 1 s and 0.08 ·10 −2 and 17.2 % for 100 s measurement was achieved respectively. As an additional validation six cases of inhomogeneous and dynamic liquid fraction distributions were investigated qualitatively. We were able to determine the liquid fraction in froth in a spatially and temporally resolved manner with a penetration depth of 9.2 cm. This investigation distinguished between two of the three froth phases within the analyzed range. However, only processes with low liquid fraction (≤ 0.83 ·10 −2 ) can be monitored. This work be considered a a first step towards in situ monitoring of froth flotation processes.

Keywords: foam; ultrasound

Permalink: https://www.hzdr.de/publications/Publ-35348
Publ.-Id: 35348


Accelerating Time-Dependent Density Functional Theory with Physics-Informed Neural Networks

Shah, K.; Cangi, A.

Time-dependent density functional theory (TDDFT) is an important method for simulating dynamical processes in quantum many-body systems. We explore the feasibility of physics-informed neural networks as a surrogate for TDDFT. We examine the computational efficiency and convergence behaviour of these solvers to state-of-the-art numerical techniques on models and small molecular systems. The method developed here has the potential to accelerate the TDDFT workflow, enabling the simulation of large-scale calculations of electron dynamics in matter exposed to strong electromagnetic fields, high temperatures, and pressures.

Keywords: physics-informed machine learning; time-dependent density functional theory

  • Lecture (Conference)
    APS March Meeting, 16.03.2022, Chicago, USA

Permalink: https://www.hzdr.de/publications/Publ-35347
Publ.-Id: 35347


RSECon22: Collaborating on the automation of research software publication with rich metadata

Bertuch, O.; Druskat, S.; Meinel, M.; Knodel, O.

Publishing your research software in a publication repository is the first step on the path to making your (research) software FAIR! But the publication of the software itself is not quite enough: To truly enable findability, accessibility and reproducibility, as well as making your software correctly citable and unlock credit for your work, your software publication must come with rich metadata to support these goals.

Keywords: HERMES; Workshop report; Research Software; Metadata

Permalink: https://www.hzdr.de/publications/Publ-35345
Publ.-Id: 35345


Bubble size distribution and electrode coverage at porous nickel electrodes in a novel 3-electrode flow-through cell

Rox, H.; Bashkatov, A.; Yang, X.; Loos, S.; Mutschke, G.; Gerbeth, G.; Eckert, K.

A novel 3-electrode cell type is introduced to run parametrical studies of H₂ evolution in an alkaline electrolyte on porous electrodes. Electrochemical methods combined with a high-speed optical measurement system are applied simultaneously to characterize the electrodes and the bubble dynamics in terms of bubble size distribution and coverage of the working electrode. Three different cathodes made of expanded nickel are investigated at applied current densities of |j| = 10 to 200 mA/cm² without forced flow and at a flow rate of 5 ml/min. The applied current density is found to significantly influence both the size of detached bubbles and the surface coverage of the working electrode. The forced flow through the cathodes is found to strongly reduce the bubble size up to current densities of about 100 mA/cm², whereas the initial transient until the cathode surface is completely covered by bubbles is only marginally affected by the flow-through.

Keywords: bubble dynamics; alkaline electrolysis; porous electrodes; machine learning; additive manufacturing; membraneless electrolyzer

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Permalink: https://www.hzdr.de/publications/Publ-35344
Publ.-Id: 35344


Lithium-Ion Battery Recycling─Influence of Recycling Processes on Component Liberation and Flotation Separation Efficiency

Vanderbruggen, A.; Hayagan, N.; Bachmann, K.; Ferreira, A.; Werner, D.; Horn, D.; Peuker, U.; Serna-Guerrero, R.; Rudolph, M.

Recycling is a potential solution to narrow the gap between the supply and demand of raw materials for lithium-ion batteries (LIBs). However, the efficient separation of the active components and their recovery from battery waste remains a challenge. This paper evaluates the influence of three potential routes for the liberation of LIB components (namely mechanical, thermomechanical, and electrohydraulic fragmentation) on the recovery of lithium metal oxides (LMOs) and spheroidized graphite particles using froth flotation. The products of the three liberation routes were characterized using SEM-based automated image analysis. It was found that the mechanical process enabled the delamination of active materials from the foils, which remained intact at coarser sizes along with the casing and separator. However, binder preservation hinders active material liberation, as indicated by their aggregation. The electrohydraulic fragmentation route resulted in liberated active materials with a minor impact on morphology. The coarse fractions thus produced consist of the electrode foils, casing, and separator. Notwithstanding, it has the disadvantage of forming heterogeneous agglomerates containing liberated active particles. This was attributed to the dissolution of the anode binder and its rehardening after drying, capturing previously liberated particles. Finally, the thermomechanical process showed a preferential liberation of individual anode active particles and thus was considered the preferred upstream route for flotation. However, the thermal treatment oxidized Al foils, rendering them brittle and resulting in their distribution in all size fractions. Among the three, the thermomechanical black mass showed the highest flotation selectivity due to the removal of the binder, resulting in a product recovery of 94.4% graphite in the overflow and 89.4% LMOs in the underflow product.

Keywords: lithium-ion battery; automated mineralogy; liberation; froth flotation; recycling

Permalink: https://www.hzdr.de/publications/Publ-35343
Publ.-Id: 35343


Simulations of Transport Phenomena in Liquid Metal Batteries

Personnettaz, P.

Liquid metal electrodes are an essential component of liquid metal batteries. The use of a liquid phase is critical for scalability, long lifetime, and high cyclability. These electrodes have a simple geometry: a liquid metal alloy is confined by an electrochemically active interface and inert walls. A mass flux is enforced at the active interface during cell operation. The liquid metal alloy experiences a local enrichment or depletion of the electroactive species. This alters the buoyancy distribution and either induces or suppresses convective flows. The quantitative analysis of an amperostatic experiment allows us to highlight the influence of this phenomenon on the cell voltage during charge and discharge. The charging step of a liquid metal battery's positive electrode is then discussed. The electroactive species (e.g., Li) is electro-refined from the alloy (e.g., Li(in Pb)), and the heavy alloy obtained at the top interface sinks down, resulting in a powerful solutal flow. The evolution of the concentration and velocity fields in 2D-axisymmetric
and 3D-cylindrical electrodes is investigated using numerical methods. Two regimes of solutal convection are recognized as a function of the Rayleigh number. We establish robust scalings for velocity and concentration differences as a function of the current density and the electrode properties. Finally, the effects of solutal convection on heat transport and mechanical coupling with the molten salt layer are highlighted.

Keywords: liquid metal battery; solutal convection; liquid metal electrode; mass transport

  • Open Access Logo Lecture (others) (Online presentation)
    International LMB Seminar, 07.10.2022, Morelia, Mexico

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Publ.-Id: 35342


Data Publication: Wash water addition on protein foam for removal of soluble impurities in foam fractionation process

Keshavarzi, B.; Krause, T.; Schwarzenberger, K.; Eckert, K.; B. Ansorge-Schumacher, M.; Heitkam, S.

the word file, the supporting information, and the excel file containing the data are attached. 

Keywords: Protein purification; foam fractionation; flotation; wash water; separation; BSA.

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Simulations of mass transport in liquid metal electrodes

Personnettaz, P.

Liquid metal electrochemical cells are electrochemical device with at least one liquid metal electrode. They were adopted in electro-metallurgical processing, heat-to-power conversion, and energy storage applications. The electrode's liquid state ensures high current density, resulting in batteries with high power densities and electro-metallurgical reactors with high conversion yields. Mass transport is critical in all liquid metal electrochemical cells, but especially in concentration cells like liquid metal batteries. These are fully liquid three-layer cells where the two electrodes are separated by a thin molten salt electrolyte. There, the positive electrode alloying and de-alloying processes store energy in the cell. Inhomogeneities in the liquid metal electrode reduce cell efficiency and material use. In this work, we are interested in understanding mass transport within this electrode. From a first study of diffusive heat and mass transport, we established that solutal effects are predominant in liquid metal electrodes. Any thermally driven convection can not significantly affect a compositionally stable stratification. A solutal flow will efficiently mix the electrode regardless of the temperature distribution. Following that, we developed a consistent explanation for the differences in the cell resistance between charge and discharge, as observed multiple times in the literature. The latter was based on quantitative analysis of a new experimental result. The voltage evolution was measured during the cycling of a liquid metal battery. During discharge, light elements are electro-deposited at the positive electrode's top interface, forming a gravitationally stable stratification. As only diffusion transports the light element away from the interface, the concentration difference and the mass transport overvoltage increase with time. During charging, the opposite phenomenon (electro-refining) takes place. The flux at the active interface builds up an unstable, asymmetric, and time-dependent buoyancy distribution in the layer. That leads first to a diffusive transient and then to a convective flow in the layer. This solutal convection was studied numerically with finite-volume and spectral-element-method solvers. The two-dimensional axisymmetric simulations performed covered Schmidt numbers from 1.125 to 288 and five orders of magnitude of flux Rayleigh numbers, starting from 10000. Two regimes were identified as a function of the flux Rayleigh number. At low Rayleigh numbers, diffusion affects the full layer height before the onset of convection. This results in a global flow. Instead, convection originates in the thin concentration boundary layer with characteristic plume structures in the high Rayleigh number regime. In this regime, onset time and concentration difference are independent with respect to the layer height. Thanks to the extensive parametric study, we retrieved robust scaling for velocity and concentration differences as a function of the current density and material properties of the layer. These results can be used in the design and operation of liquid metal electrodes. For example, they allow estimating the mass transport overvoltage during charge. Furthermore, we studied numerically solutal convection in three-dimensional cylindrical electrodes. We showed that the two-dimensional approximation captures quite remarkably the evolution of integral quantities observed in fully three-dimensional simulations. This is not due to the axisymmetric nature of the flow. On the contrary, we observed a rich dynamic, with polygonal-shaped cells forming and evolving in the active interface concentration distribution. Finally, the influence of non-uniform current distribution on mass transport in a liquid metal electrode was investigated. Differences with respect to the homogenous configuration are present in pure diffusion and at the onset of convection. The solutal flow is able to reduce the inhomogeneities in the electrode.

Keywords: liquid metal battery; mass transport; solutal convection; liquid metal electrode

Permalink: https://www.hzdr.de/publications/Publ-35340
Publ.-Id: 35340


Weight values for MCNP calculations based on Recursive Monte-Carlo method

Yadav, P.; Rachamin, R.; Konheiser, J.

Radiation shielding calculations are widely performed using the Monte-Carlo N-Particle Transport (MCNP) code. Such calculations are typically associated with deep penetration problems, which involve the transportation of particles through thick geometric systems. In such systems, particles barely reach the focus zone, also known as the tally region, resulting in few events and increased uncertainty in the calculation outputs. Increasing the number of source particles can enhance the calculation precision, but this limits the computational efficiency, as it is difficult to simulate too many particles at a reasonable computing time. For complex geometries, an analog Monte-Carlo calculation takes many days or weeks to obtain a statistically reliable result. Hence, there are other methods besides increasing computational time to improve the calculation efficiency. These methods are called variance reduction techniques. The basic idea behind such techniques is to produce statistically precise results with minimal computational effort by increasing sampling in areas of interest and decreasing sampling in areas that contribute less to tallies. There are various variance reduction techniques available in the MCNP code. However, these techniques must be used judiciously, and their effects must be monitored using the summary information provided by a Monte Carlo run. The weight-window (WW) is one of the effective variance reduction techniques. The goal of this method is to use particle weights to increase the number of countable events in the focus tally with the same number of sources. The particle weights are controlled by either splitting or Russian roulette, depending on the local cell weights. Each of the cells has a weight-window that is defined by lower and upper weight bounds. Particles crossing the upper weight bound are split, and particles falling below the lower bound are rouletted such that all the particles lie within the window bounds. These weight window parameters can be inserted manually or calculated by MCNP’s built-in weight-window generator (WWG). With complex geometries, manual input is very difficult and reaches statistical limits. As a rule, the generator must be used iteratively to generate desirable weights in the cells according to the task. To speed up this process, we focus on the development of optimal weight parameters based on the Recursive Monte Carlo (RMC) method. This method is used in the TRAWEI code to generate weights for the Monte-Carlo code TRAMO. Both codes were developed at HZDR. With TRAWEI, a set of optimal weights can be generated in a single computational step with a relatively short time and minimum effort. In this study, we compared and analyzed the results of a single material problem using weights generated by MCNP’s standard weight window generator (WWG) and weights generated by TRAWEI.

Keywords: Deep penetration problems; Weight-window; Recursive Monte Carlo; MCNP; TRAWEI

  • Contribution to proceedings
    14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection and Shielding Division, 11.06.2022, Seattle, WA, United States
    Proceedings of the 14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection

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Publ.-Id: 35339


Investigation of uranium(VI) reduction by the repository-relevant bacterium Desulfosporosinus hippei DSM 8344T

Hilpmann, S.; Steudtner, R.; Drobot, B.; Hübner, R.; Cherkouk, A.

INTRODUCTION
For a comprehensive safety assessment regarding the deep geological disposal of high-level radioactive waste, various aspects have to be taken into account. Besides geological, geochemical, and geophysical properties, the influence of naturally occurring microorganisms in the surrounding host rock and backfill material play a crucial role in the environment of such a repository. Clay formations are potential host rocks for the long-term storage of this waste, whereas bentonites are supposed to serve as backfill material, not only for a final disposal site in clay formations but also in crystalline rock. In the event of a worst-case scenario, if water enters the disposal site, radionuclides can escape from the waste canisters and thus interact with the microorganisms. This can, for example, lead to changes in the chemical speciation or the oxidation state of the metal ions.
RESULTS & DISCUSSION
Under repository-relevant conditions, Desulfosporosinus spp. are important representatives of anaerobic, sulfate-reducing bacteria being present in clay formations as well as in bentonites. Various studies show that they are playing a major role in the microbial communities of these surroundings. A closely related microorganism to the isolated species is Desulfosporosinus hippei DSM 8344T. Therefore, this bacterium was used to investigate its interactions with uranium(VI) especially regarding the reduction to the less-mobile uranium(IV) having favorable properties like a reduced mobility.
Time-dependent reduction experiments showed the removal of about 80% of the uranium(VI) from the supernatants in artificial Opalinus Clay pore water (100 µM uranium(VI), pH 5.5) within 48 h. Corresponding UV/Vis measurements of the dissolved cell pellets provide clear proof of the formed uranium(IV). The proportion of this oxidation state in the cell-bound uranium increases up to 40% after one week. Therefore, a combined sorption-reduction process is a possible interaction mechanism.
Time-resolved laser-induced luminescence spectroscopy reveals the presence of two uranium(VI) species in the supernatant. A comparison with reference spectra leads to an assignment to a uranyl(VI) lactate and a uranyl(VI) carbonate complex. The species distribution shows a decrease of the proportion of the lactate species with time, whereas the proportion of the carbonate species remains almost constant.
Uranium aggregates are formed on the cell surface during the process, as determined by scanning transmission electron microscopy (STEM). Furthermore, cells release uranium-containing vesicles as a possible defense mechanism against cell encrustation.
CONCLUSIONS
The findings of this study help to close existing gaps in a comprehensive safeguards concept for a repository for high-level radioactive waste in clay rock. Moreover, this study provides new insights into the interactions of sulfate-reducing microorganisms with uranium(VI) and thus, contributes to new bioremediation approaches of radionuclide-contaminated environments, as well.

Keywords: Uranium(VI) reduction; Sulfate-reducing bacteria; Opalinus Clay pore water

  • Poster
    Microbial Technology Week, 07.-11.11.2022, Ljubljana, Slowenien

Permalink: https://www.hzdr.de/publications/Publ-35338
Publ.-Id: 35338


Self-healable printed magnetic field sensors using alternating magnetic fields

Xu, R.; Canon Bermudez, G. S.; Pylypovskyi, O.; Volkov, O.; Oliveros Mata, E. S.; Zabila, Y.; Illing, R.; Makushko, P.; Milkin, P.; Ionov, L.; Faßbender, J.; Makarov, D.

We employ alternating magnetic fields (AMF) to drive magnetic fillers actively and guide the formation and self-healing of percolation networks. Relying on AMF, we fabricate printable magnetoresistive sensors revealing an enhancement in sensitivity and figure of merit of more than one and two orders of magnitude relative to previous reports. These sensors display low noise, high resolution, and are readily processable using various printing techniques that can be applied to different substrates. The AMF-mediated self-healing has six characteristics: 100% performance recovery; repeatable healing over multiple cycles; room-temperature operation; healing in seconds; no need for manual reassembly; humidity insensitivity. It is found that the above advantages arise from the AMF-induced attraction of magnetic microparticles and the determinative oscillation that work synergistically to improve the quantity and quality of filler contacts. By virtue of these advantages, the AMF-mediated sensors are used in safety application, medical therapy, and human-machine interfaces for augmented reality.

Keywords: printed electronics; healable magnetic field sensors; magnetic composites

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Permalink: https://www.hzdr.de/publications/Publ-35334
Publ.-Id: 35334


Accelerator mass spectrometry measurements of 93Zr for astrophysical and nuclear technology applications

Pavetich, S.; Wallner, A.; Bottero, H.; Fifield, L. K.; Froehlich, M. B.; Huang, Y.; Koll, D.; Révay, Z.; Slavkovská, Z.; Sterba, J. H.; Tims, S. G.

Zirconium-93 is a long-lived radionuclide with a half-life of (1.61 ± 0.05) × 106 yr. Production cross sections for 93Zr by neutron capture on stable 92Zr in the keV and thermal energy ranges are important input parameters for astrophysical network calculations and nuclear industry, respectively. Despite their importance, existing experimental data suffer from large uncertainties. Here, the combination of neutron activation and accelerator mass spectrometry (AMS) is presented as an alternative method to online time-of-flight measurements for the determination of these cross sections. The main challenges for AMS of 93Zr are the interference from the stable isobar 93Nb and the production of suitable reference material. At the Heavy Ion Accelerator Facility (HIAF) the first challenge is tackled with the available high particle energies and by investigating different Zr compounds and extracted molecular beams. Using ZrF5− beams extracted from ZrF4 sample material, it is shown that the Nb background can be reduced by up to two orders of magnitude relative to the extraction of ZrO− beams from ZrO2. Using the 13+ charge state and particle energies of ∼190 MeV, 93Zr/Zr background levels in the 10−12 range are regularly achieved at HIAF. The ZrF5− output from ZrF4 samples may be highly variable but can be stabilised using an intimate mixture of ZrF4 and PbF2 at a ratio of 1:10 that has been dried down from a concentrated hydrofluoric acid solution. An option to produce a well-characterised 93Zr reference material by utilising the well-known 235U-fission yield of 93Zr is discussed. Once this remaining challenge is resolved, accurate measurements of the astrophysically and technologically relevant neutron-capture cross sections of 92Zr using AMS will be possible at HIAF.

Keywords: Accelerator mass spectrometry of 93Zr; Accelerator mass spectrometry reference material; Isobar suppression

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Publ.-Id: 35332


Electrical and Thermal Conductivity of High-Pressure Solid Iron

Ramakrishna, K.; Lokamani, M.; Baczewski, A.; Vorberger, J.; Cangi, A.

We study the electrical and thermal conductivity of iron at high pressures using time-dependent density functional theory. In doing so, we particularly consider the impact of a Hubbard correction (+\textit{U}) specifically for regions where strong electron correlations are present. Using the TDDFT+U methodology, we examine the anisotropy in the thermal conductivity of HCP iron, which may provide insights into the transport properties at conditions relevant to the core-mantle boundary and the interior of the Earth.

Keywords: Matter under Extreme Conditions; Time-dependent DFT; Computational Physics

Permalink: https://www.hzdr.de/publications/Publ-35330
Publ.-Id: 35330


Magnetic induction processes in hot Jupiters, application to KELT-9b

Dietrich, W.; Kumar, S.; Poser, A. J.; French, M.; Nettelmann, N.; Redmer, R.; Wicht, J.

The small semimajor axes of hot Jupiters lead to high atmospheric temperatures of up to several thousand Kelvin. Under these conditions, thermally ionized metals provide a rich source of charged particles and thus build up a sizeable electrical conductivity. Subsequent electromagnetic effects, such as the induction of electric currents, Ohmic heating, magnetic drag, or the weakening of zonal winds have thus far been considered mainly in the framework of a linear, steady-state model of induction. For hot Jupiters with an equilibrium temperature Teq > 1500 K, the induction of atmospheric magnetic fields is a runaway process that can only be stopped by non-linear feedback. For example, the back-reaction of the magnetic field on to the flow via the Lorentz force or the occurrence of magnetic instabilities. Moreover, we discuss the possibility of self-excited atmospheric dynamos. Our results suggest that the induced atmospheric magnetic fields and electric currents become independent of the electrical conductivity and the internal field, but instead are limited by the planetary rotation rate and wind speed. As an explicit example, we characterize the induction process for the hottest exoplanet, KELT-9b, by calculating the electrical conductivity along atmospheric P-T profiles for the dayside and nightside. Despite the temperature varying between 3000 and 4500 K, the
resulting electrical conductivity attains an elevated value of roughly 1 S/m throughout the atmosphere. The induced magnetic fields are predominately horizontal and might reach up to a saturation field strength of 400 mT, exceeding the internal field by two orders of magnitude.

Keywords: magnetic fields; plasmas; exoplanet; atmospheres – planets and satellites

  • Open Access Logo Monthly Notices of the Royal Astronomical Society 517(2022), 3113-3125
    Online First (2022) DOI: 10.1093/mnras/stac2849
    arXiv: https://arxiv.org/abs/2210.03351

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Publ.-Id: 35329


Seed-Mediated Synthesis of Photoluminescent Cu−Zn−In−S Nanoplatelets

Bora, A.; Prudnikau, A.; Fu, N.; Hübner, R.; Borchert, K. B. L.; Schwarz, D.; Gaponik, N.; Lesnyak, V.

Ternary and quaternary colloidal nanocrystals (NCs) based on I−III−VI group semiconductors are promising low-toxic luminescent materials attracting huge interest as alternatives to cadmium- and lead-chalcogenide-based NCs. Despite significant progress in the synthesis of three-dimensionally confined quantum dots based on I−III−VI semiconductors with intensive photoluminescence (PL) in a broad spectral range, all attempts to prepare one-dimensionally confined nanoplatelets (NPLs) or nanosheets have resulted in rather nonemitting two-dimensional (2D) NCs. Since 2D NCs of the II−VI group exhibit unique anisotropic optical properties, exploring synthetic strategies to obtain 2D I−III−VI-based NPLs might also reveal interesting optical and electronic features. In this work, we demonstrate the synthesis of luminescent In-rich Cu−Zn−In−S (CZIS) NPLs using a one-pot approach. The synthesis includes the formation of
Cu−In−S NPLs from In2S3 seeds, followed by the incorporation of zinc to form quaternary NPLs with improved stability and optical properties. The synthetic strategy implemented results in the formation of ∼1 nm thick NPLs with lateral sizes of ∼30 × 10 nm2 and a tetragonal crystal structure. As-synthesized NPLs are stable at ambient conditions and demonstrate PL in the range of 700−800 nm with a large Stokes shift. An additional shell of ZnS grown on CZIS NPLs resulted in the enhancement of their PL quantum yield reaching 29%.

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Permalink: https://www.hzdr.de/publications/Publ-35326
Publ.-Id: 35326


CMOS compatible manufacturing of a hybrid SET-FET circuit

Del Moral, A.; Amat, E.; Engelmann, H.-J.; Pourteau, M.-L.; Rademaker, G.; Quirion, D.; Torres-Herrero, N.; Rommel, M.; Heinig, K.-H.; von Borany, J.; Tiron, R.; Bausells, J.; Perez-Murano, F.

This study analyzes the CMOS compatibility in the manufacturing of a hybrid SET-FET circuit. The fundamental element towards an operating SET at room temperature is a vertical nanopillar with embedded Si nanodot generated by ion-beam irradiation. The integration process from nanopillars to contacted SETs is validated by structural characterization. Then, the monolithic fabrication of planar FETs co-integrated with vertical SETs is presented, and its compatibility with standard CMOS technology is demonstrated. The work includes process optimization, pillar integrity validation, electrical characterization and simulation taking into account parasitic elements. The FET fabrication process is adapted to meet the requirements of the pre-fabricated nanopillars. Overall, this work establishes the groundwork for the realization of a hybrid SET-FET circuit operating at room temperature.

Keywords: CMOS; MOSFET; vertical nanopillar; single electron transistor; hybrid circuit

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Permalink: https://www.hzdr.de/publications/Publ-35323
Publ.-Id: 35323


Microscopic liquid-gas interface effect on liquid wetting

Zhang, J.; Ding, W.; Wang, Z.; Wang, H.; Hampel, U.

Hypothesis: Young contact angle is widely applied to evaluate liquid wetting phenomena on solid surfaces. For example, it gives a truncated-spherical shape prediction of a droplet profile through the Young-Laplace equation. However, recent measurements have shown deviations between microscopic droplet profiles and the spherical shape, indicating that the conventional Young contact angle is insufficient to describe microscopic wetting phenomena. In this work, we hypothesize that a liquid-gas interface nano-bending, which is caused by the nonlinear coupling between the effects of the microscopic interface geometry and solid-liquid interactions, is responsible for this deviation.
Simulation and theory: Using molecular dynamics simulations and mathematical modeling, we reveal the structure of the nano-bending and the mechanism of the nonlinear-coupled effect. We further apply our findings to illustrate a liquid microlayer with the saddle-shaped profile in nucleate boiling.
Findings: The nonlinear-coupled effect is responsible for the deviation of a nano-droplet profile and also the very thin microlayer captured by different experiments. The saddle-shaped interface significantly highlights the nonlinear-coupled effect. The interface nano-bending, rather than the Young contact angle, acts as the boundary condition and dictates the liquid wetting system, especially for the case with high interface curvature. These findings provide insight into recent nano-scale droplet- and bubble-related wetting phenomena.

Keywords: liquid wetting; nano-bending; nonlinear-coupled effect; interface curvature; Young contact angle; nano-droplet; nano-bubble; microlayer; nucleate boiling

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Permalink: https://www.hzdr.de/publications/Publ-35321
Publ.-Id: 35321


Si nanostructure formation in quenched AlSi µ-droplets for application as anode material in lithium-ion-batteries

Tucholski, D.; Heinig, K.-H.

We report on 3D lattice kinetic Monte Carlo (3DlkMC) simulation of nanostructure formation during rapid quenching in gas-atomization (up to 108K/s) of droplets of AlSi alloy melt. The nanostructured Si particles (with the Al selectively etched away) promise to enable about 10x the capacity of the current state-of-the-art graphite in lithium-ion batteries by mitigating Si pulverization.

This work reproduces the experimentally found nanosponge and core-shell particles and reveals heteronucleation at Al2O3 sites resulting from trace oxygen at the surface as the formation mechanism for core-shell particles.

The computer simulation uses a memory-efficient bit-encoded lattice, enabling large scale atomistic calculations, while kinetics is implemented via CPU-efficient bit-manipulation for atom jumps between lattice sites. The jump probabilities are described by the metropolis algorithm with a look-up-table of energies calculated with an angular dependent potential for the Si-Al-Au system in LAMMPS.

This work is supported by the federal ministry for economic affairs and climate protection under grant number 01221755/1.

Keywords: Lithium-Ion-Batteries; Modelling and Simulation; Quenching

  • Lecture (Conference)
    Verhandlungen der Deutschen Physikalischen Gesellschaft e.V., 05.-09.09.2022, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35318
Publ.-Id: 35318


Modelling of AlSi droplet quenching Nano-Si for battery anodes

Tucholski, D.; Faßbender, J.; Engelmann, H.-J.; Heinig, K.-H.

Robis requires an Abstract, but this poster doesn't have one, so here's the one from a conference talk about the same contents:

We report on 3D lattice kinetic Monte Carlo (3DlkMC) simulation of nanostructure formation during rapid quenching in gas-atomization (up to 108K/s) of droplets of AlSi alloy melt. The nanostructured Si particles (with the Al selectively etched away) promise to enable about 10x the capacity of the current state-of-the-art graphite in lithium-ion batteries by mitigating Si pulverization.

This work reproduces the experimentally found nanosponge and core-shell particles and reveals heteronucleation at Al2O3 sites resulting from trace oxygen at the surface as the formation mechanism for core-shell particles.

The computer simulation uses a memory-efficient bit-encoded lattice, enabling large scale atomistic calculations, while kinetics is implemented via CPU-efficient bit-manipulation for atom jumps between lattice sites. The jump probabilities are described by the metropolis algorithm with a look-up-table of energies calculated with an angular dependent potential for the Si-Al-Au system in LAMMPS.

This work is supported by the federal ministry for economic affairs and climate protection under grant number 01221755/1.

Keywords: Poster; Quenching; Simulation and Modelling; Lithium-Ion-Batteries

  • Poster
    DocSeminar22, 19.-21.10.2022, Wroclaw, Polen

Permalink: https://www.hzdr.de/publications/Publ-35317
Publ.-Id: 35317


Influences of oil collector on surface air nucleation in fine graphite flotation

Xu, M.; Haijun, Z.; Rudolph, M.

This paper investigates the effect of an oil collector, namely diesel oil, on surface air nucleation and the influence of
nucleation microbubbles on collector adsorption in froth flotation. In order to prepare the condition for air nucleation in
flotation, air-oversaturated water was produced using tap water pressurized by high-pressure air in an autoclave. Microflotation,
single bubble collision experiments, contact angle measurements, microscopic observations, and agglomerations
analysis were combined to investigate the effects of the oil collector on air nucleation and agglomerates formation.
Furthermore, the free energy changes in an ideal system were utilized to explain the mechanisms. The experimental results
and free energy changes show that diesel oil can improve the air nucleation probability on graphite surfaces by decreasing
the barrier for nucleation. Meanwhile, the oil collector can also significantly increase the fraction of agglomerates formed in
air-oversaturated water to improve the recovery of fine particles. Besides, the results indicate that the formation of nucleation
microbubbles before collector conditioning can occupy significant surface areas of the graphite particles and inhibit the
collector adsorption on the mineral surfaces.

Keywords: Agglomerations; Air nucleation; Air-oversaturated water; Oil collector

Permalink: https://www.hzdr.de/publications/Publ-35316
Publ.-Id: 35316


Quantification of the impact of defect density
on dissolution rate and nanotopography on
 alpha particle irradiated biotite crystals

Cardenas Rivera, M. A.

Alpha particles emitted from actinides can cause lattice defects in crystalline solids. These affect surface reactivity of various reactions such as dissolution, growth or sorption1. Biotite is an important rock-forming mineral in a variety of igneous and metamorphic rocks that are considered for use as deep geological repositories. The frequent occurrence of biotite in host-rocks can quantitatively influence the retention of migrating radionuclides in the far field2. Therefore, understanding and quantifying the effects exposure to radionuclides can have on the sorbing capabilities of a crystal, will lead to an improved predictability of the far-field natural barriers upon which safe waste disposal relies. In this study, we investigate the formation of crystal defects in biotite and their influence on surface reactivity. For this, two pristine biotite samples were irradiated with and 4He3+ focused ion beam in order to induce crystal structural damage. This is an analogue to the situation of radionuclide release in the repository. The irradiation parameters were chosen to avoid amorphization and to focus on crystal defect development. The samples are them surface-controlled dissolved to finally quantify the defect density by using vertical scanning interferometry (VSI). Subsequently, the surface-modified biotite samples are used for sorption experiments witch actinide analogues such as 152EU3+. Comparison of the anticipated results will provide conclusions about the quantitative changes in reactive transport processes of actinide migration in sheet-bearing host rocks.

Related publications

  • Poster
    Actinides Revisited - 2022, 21.-23.09.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35313
Publ.-Id: 35313


Knowledge Management (KM) in Radioactive Waste Management (RWM)

Abbasova, D.; Hoefer, G.; Arnold, T.; Wanka, S.; Franzen, C.; Wellmann, P. L.

KM is the process through which organizations generate value from their intellectual and knowledge-based assets 1.
Implementation of Knowledge Management (KM) is an important issue for all types of nuclear organizations and in particular for Radioactive Waste Management (RWM) organizations. Thus, the fundamental objective of RWM is to manage the radioactive waste without adverse impact for human health and the environment during its radioactive waste lifetime. Considering the life cycle of the radioactive waste it is obvious that KM accompanies Safety Management (SM). The management of radioactive waste affects future generations and covers pretreatment, treatment, conditioning, storage and disposal. At all mentioned stages operators are dealing with information such as take the records, use the standards & templates, prepare the reports. Without adequate knowledge it would be impossible to carry out this work and conclusively safety will be under risk. It is clear, that managing the knowledge must be implemented at all stages of RWM with the integration of knowledge processes concentrating on the following four core activities:

  • To generate the knowledge
  • To store the knowledge
  • To share the knowledge
  • To distribute the knowledge

and will be focused on
  • Information and Document Management
  • Human Resource Management
  • Knowledge Organizational Structure

However, depending on the organization (Regulatory, Operations, R&D organizations) involved in RWM the used KM methods & tools will be different. Nuclear R&D organizations can be categorized into seven types oriented on types of functions undertaken by the respective organization. In 2012 IAEA2 has classified them as follows: (1.) Basic research functions, (2.) Applied research functions, (3.) Design R&D functions, (4.) Functions utilizing nuclear R&D facilities, (5.) Functions utilizing non-nuclear R&D facilities, (6.) Educational R&D functions and (7.) Technical support & service functions.
Referring to R&D functions it becomes obvious that out of seven known Knowledge levels3 R&D organizations mainly use four (i.e. Organizational memory, Knowledge in Processes, Knowledge in Products & Services and Knowledge in People). An example for this is the KM initiatives in the Institute of Resource Ecology.
The Institute of Resource Ecology is one of eight institutes of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) where many administrative tasks are centralized. For example the human resources (HR) department, the financial department, the international department and the IT department are all administrated centrally by the HZDR. The HZDR has an internal platform which is used for administrative work, data & information management, communication and keeps employees updated with ongoing and upcoming activities in their institutes. Beside this platform, HZDR employees use different IT tools, e.g. Outlook, Mattemost, etc, for close cooperation. The employees skill development program is administrated by the center. This program follows the requirements collected from all HZDR employees.
Continuous education and training programs for the HZDR employees and students, well organized in cooperation with partner organizations (TU-Dresden etc) do also support the knowledge capturing & sharing process.
The centralized library has more than 40.000 books in hard copy and 16.300 e-books & journals and all are available for employees of the center. The repository of HZDR’s publications has more than 36.000 scientific papers. In addition, each institute has also an internal scientific database for employee’s needs.
There are several formats of information and knowledge exchange in the Institute. To convince the employees of the importance of knowledge-sharing the institute provides series of different workshops regularly e.g. monthly seminars, workshops, department meetings, strategy and jour-fixe meetings in hybrid formats.
Obviously, the critical knowledge in the institute is linked to research works. The critical knowledge here is defined as knowledge which is needed to meet the objectives of the Institute. The critical knowledge holders are well known. There are several practices applied in the institute for maintaining the knowledge and transfer it. First of all to mention here is the supervision & mentoring program for the PhD students by critical knowledge holders. Another one is the procedure for uploading publications and records to the internal repository. There are also two inhouse scientific databases at the IRE available for internal and external users: (1.) RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics and database and (2.) the Thermodynamic Reference Database (THEREDA). However, there is still a high demand for the development of Knowledge Preservation programs. The loss of knowledge in association with the retirement of knowledge holders is still an issue in the institute. This is true for all nuclear organizations.
Different approaches have been used in industry. As an example, the approach applied by the Federal Company for Radioactive Waste Disposal (BGE) is described.
Due to the restructuring of the nuclear waste-management landscape in Germany, BGE is since 2017 the national competence centre in Germany and responsible for the disposal of radioactive waste.
For many decades, Research &Developement-work for this subject has been performed in Germany with an enormous stock of knowledge (topical and quantitative), but an overview is impaired due to the diffuse and local organisation of knowledge of the nuclear waste-management landscape.
Research reports for example can be found in many archives, but no archive is complete and „Old stock of knowledge“(old documents, grey literature) has to be embedded in the new stock of knowledge.
At the same time the imminent loss of expertise due to phasing out of nuclear energy production and mining in Germany must be considered as a limiting and partially critical factor, especially while reflecting the age structure of the BGE-staff and the restart of the new site selection procedure for disposal of highly radioactive waste products.
Facing these prerequisites the newly formed internal department for knowledge management (KM) of the BGE is establishing an infrastructure for KM and generates a connection between KM platforms and knowledge holders in the company to make explicit, implicit and tacit knowledge available.
The approach for the explicit knowledge is the provision of a digital information basis, into which current results from research and development are entered as a knowledge store. This knowledge store currently consists of more than 16.000 documents, mainly research reports and scientific publications, which are concerned with diverse topics for the final disposal of radioactive waste.
The total stock of available internal company documents can be accessed with a browser-based text analysis software. Intelligent search algorithms render the textual contents accessible, combine them with synonyms and dictionaries deposited in the system and make the resulting hits of the search queries available for the user in order of importance in summarized and full text versions.
Using specific query terms the software analyzes the available documents of the digital information basis and provides a brief description of the contents, the naming of relevant keywords, the identification of sources, compilers, institutions, knowledge carriers and an extended optimized information analysis of hits, as well as the possibility to access the complete document. The search options can be combined with established internet search engines as well as with queries of incorporated information or databank catalogue of national and international scientific institutions or libraries, which are concerned with research programs relevant for repositories4. The content volume of the digital information basis, as well as the amount of externally connected research sources is permanently growing.
To further increase and optimize the information possibilities for employees of the BGE and to make implicit knowledge partly available, a variety of general and demand-oriented interactive knowledge maps have been and will be implemented in the intranet, which enable specific queries on topics, expert information, etc.
To capture the tacit knowledge of persons who are leaving the company due to retirement, concerted concepts, e.g. interviews including transcriptions are used to make this individual knowledge available to the BGE-staff using the BGE internal tools for capturing and distributing implicit and explicit knowledge.
Additional actions contain, e.g. the initiation and organisation of technical and professional talks on various topics and to establish them as a permanent and important exchange possibility in the company.
While “How to use” seminars for the use of the broser-based text analysis software are already established and a permanent and reoccurring part in the company, further seminars and videos with “How to use” approach e.g. for demand-oriented interactice knowledge maps are in the implementations process as well as a Podcast series about Knowledge Management in the BGE.
For the further development of person-related and further group-related knowledge, the BGE Knowledge Management group/department is compiling concepts, which can only be implemented together with the employee in the company and its own guiding principles as they border on certain interfaces in the organization/company, taking into account that all measures to share and distribute knowledge can only be a permanent success if it is voluntarily process without compulsion.
By writing this paper we tried to illustrate the practical difference between KM initiatives in R&D and industry. However, the overlapping of the approaches at some certain stages are visible. The information management has been considered as an essential part of the knowledge management in both of organizations. The capture of the critical knowledge in both organizations remains a main issue even if the selected methods are different. The coaching & mentoring program which are well implemented at the IRE (HZDR), are may be difficult to realize/accomplish at the BGE. However, the pilot coaching program is planned at the BGE, but currently not available due to the “young” founding date in 2017. One of the main concerns of the BGE as an implementer, is the motivation and encouragement of all employees to share and distribute their knowledge and benefit from each other.

Reference:

1. SANTOSUS, MEGAN, and SURMACZ, The ABCs of Knowledge Management, Knowledge Management Research Center, accessed on 09 December 2005 at http://www.cio.com/research/knowledge/edit/kmabcs.html. )
2. IAEA, Knowledge Management for nuclear Research and Development organizations IAEA, Vienna, 2012
3. Jatinder N.D. Gupta, Sushil K. Sharma, Jeffrey Hsu, “An overview of Knowledge Management”, Knowledge management. I. Jennex, Murray E., 1956
4. Gunnar Hoefer, Sebastian Wanka, Peter L. Wellmann, Knowledge Management in the Federal Company for Radioactive Waste Disposal (BGE), Saf. Nucl. Waste Disposal, 1, 251–253, 2021

Keywords: Knowledge Management; RWM; Knowledge capture; Information management

  • Lecture (Conference)
    17th International Conference on Knowledge Management 2022, 23.-24.06.2022, Potsdam, Germany
  • Contribution to proceedings
    17th International Conference on Knowledge Management, 23.-24.06.2022, Potsdam, Germany
    Proceedings 17th International Conference on Knowledge Management

Permalink: https://www.hzdr.de/publications/Publ-35311
Publ.-Id: 35311


Longitudinal and multimodal radiomics models for head-and-neck cancer outcome prediction

Starke, S.; Zwanenburg, A.; Leger, K.; Zöphel, K.; Kotzerke, J.; Krause, M.; Baumann, M.; Troost, E. G. C.; Löck, S.

Radiomics analyses provide a promising avenue for enabling personalized radiotherapy. Most frequently, prognostic radiomics models are based on features extracted from medical images that are acquired before treatment. Here, we investigate whether combining data from multiple timepoints during treatment and additionally from multiple imaging modalities can improve the predictive ability of radiomics models.
We extracted radiomics features from computed tomography (CT) images acquired before treatment as well as two and three weeks after the start of radiochemotherapy for 55 patients with locally advanced head and neck squamous cell carcinoma (HNSCC). Additionally, we obtained features from FDG-PET images taken before treatment and three weeks after start of therapy. Cox proportional hazards models were then built based on features of the different image modalities, treatment timepoints and combinations thereof using two different feature selection methods in a five-fold cross-validation approach. Based on the cross-validation results, feature signatures were derived and their performance was independently validated. Discrimination regarding loco-regional control was assessed by the concordance index (C-index) and log-rank tests were performed to assess risk stratification.
The best prognostic performance was obtained for timepoints during treatment for all modalities. Overall, CT was the best discriminating modality with an independent validation C-index of 0.78 for week two and week two and three combined. However, none of these models achieved a statistically significant patient stratification. Models based on FDG features from week three provided both, satisfactory discrimination (C-index=0.61 and 0.64) and a statistically significant stratification (p=0.044 and p<0.001) but produced highly imbalanced risk groups.
After independent validation on larger data sets, the value of (multimodal) radiomics models combining several imaging timepoints should be prospectively assessed for personalized treatment strategies.

Keywords: radiomics; head-and-neck cancer; loco-regional control; survival analysis; computed tomography; positron emission tomography; cox proportional hazards; longitudinal imaging

Permalink: https://www.hzdr.de/publications/Publ-35309
Publ.-Id: 35309


Experimental Investigations and Numerical Assessment of Liquid Velocity Profiles and Turbulence for Single- and Two-phase Flow in a Constricted Vertical Pipe

Tas-Köhler, S.; Neumann-Kipping, M.; Liao, Y.; Bieberle, A.; Hampel, U.

In this work, the capabilities of state-of-the-art turbulence models are compared for a three-dimensional flow (3D) field within a constricted vertical pipe. The considered flow domain is a vertical pipe section with a baffleshaped flow constriction which leads to the development of a jet flow through and a recirculation flow region behind the constriction. Different Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) models were tested for single- and two-phase flow simulations. In the two-phase simulations, bubble-induced turbulence (BIT) was also considered by adding source terms in the k and ε/ω equations. The results are validated against experimental data. We employed hot-film anemometry (HFA) for liquid velocity measurement and
combined it with ultrafast X-ray computed tomography (UFXCT), which provides gas phase data. Based on the local phase-indicator function obtained from the tomographic image data, we can correct HFA signals, which become corrupted by bubble contacts. We found that for single-phase flow all RANS models predict axial velocity well while radial velocity prediction is inadequate. LES models, however, achieve a better prediction of the latter. For two-phase flow, the axial component of the liquid velocity is well captured by all RANS models and the radial component of the liquid velocity is predicted better than for single-phase flow. In general, the computationally less costly RNG k-ε model performs similar to the SSG RSM model and can therefore be recommended for simulation of complex flow scenarios.

Keywords: Bubbly two-phase flow; Computed tomography; Hot-film anemometry; Liquid velocity; Turbulent kinetic energy; CFD modelling

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  • Secondary publication expected from 09.08.2023

Permalink: https://www.hzdr.de/publications/Publ-35307
Publ.-Id: 35307


Flexible and printable magnetoelectronics for human-machine interfaces and soft robotics

Makarov, D.

In this presentation, I will review our recent activities on flexible and printed magnetic field sensorics.

Keywords: flexible magnetic field sensors; printable magnetic field sensors; magnetic soft robots; human-machine interfaces

Related publications

  • Lecture (others)
    Seminar at the University Bolzano, 25.11.2022, Bolzano, Italy

Permalink: https://www.hzdr.de/publications/Publ-35306
Publ.-Id: 35306


Scripts and Models for "Predicting electronic structures at any length scale with machine learning"

Fiedler, L.; Schmerler, S.; Modine, N.; Vogel, D. J.; Popoola, G. A.; Thompson, A.; Rajamanickam, S.; Cangi, A.

Scripts and Models for "Predicting the Electronic Structure of Matter on Ultra-Large Scales"

This data set contains scripts and models to reproduce the results of our manuscript "Physics-informed Machine Learning 
Models for Scalable Density Functional Theory Calculations". The scripts are supposed to be used in conjunction
with the ab-initio data sets also published alongside our research article. 

Requirements

python>=3.7.x
mala>=1.1.0
ase
numpy

Contents

| Folder name      | Description                                      |
|------------------|--------------------------------------------------|
| data_analysis/   | Run script for RDF calculations        |
| model_inference/ | Run script to run inference based on MALA models |
| model_training/  | Run script to train MALA models                  |
| trained_models/  | Trained models for beryllium and aluminium       |

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Permalink: https://www.hzdr.de/publications/Publ-35305
Publ.-Id: 35305


High Dielectric Transparent Film Tailored by Acceptor and Donor Codoping

Huang, D.; Shi, Y.; Younas, M.; Tahir Ali Khan, R.; Nadeem, M.; Shati, K.; Harfouche, M.; Kentsch, U.; Liu, Z.; Li, Y.; Zhou, S.; Kuznestov, A.; Chi-Chung Ling, F.

High dielectric constant materials are of particular current interests as indispensable components in transistors, capacitors, etc. In this context, there are emerging trends to exploit defect engineering in dielectric ceramics for enhancing the performance. However, demonstrations of similar high dielectric performance in integration-compatible crystalline films are rare. Herein, such a breakthrough via the functionalization of donor–acceptor dipoles by compositional tuning in GaCu codoped ZnO films is reported. The dielectric constant reaches ~200 at 1 kHz and the optical transmittance in visible light reaches ~80%. Importantly, by analyzing the impedance spectroscopy data, prominent relaxation mechanisms in correlation with the dipole properties, enabling consistent explanations of the dielectric constant as a function of frequency are discriminated. The atomistic nature of the dipoles is revealed by the systematic X-ray spectroscopy analysis. Spectacularly, similar trends for the dielectric properties are observed, while synthesizing samples by pulsed laser deposition and ion implantation, indicating the general character of the phenomena.

Related publications

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  • Secondary publication expected from 18.10.2023

Permalink: https://www.hzdr.de/publications/Publ-35303
Publ.-Id: 35303


Sensitive multi-element profiling with high depth resolution enabled by time-of-flight recoil detection in transmission using pulsed keV ion beams

Holeňák, R.; Lohmann, S.; Primetzhofer, D.

The potential of time-of-flight recoil detection for sensitive multi-element profiling of thin membranes and quasi-2D systems in transmission geometry using pulsed keV ion beams is assessed. While the time-of-flight approach allows for simultaneous detection of multiple elements, to the largest extent irrespective of recoil charge states, the keV projectile energies guarantee high recoil-cross sections yielding high sensitivity at low dose. We demonstrate the capabilities of the approach using 22Ne and 40Ar as projectiles transmitted through thin carbon foils featuring optional LiF-coatings and single-crystalline silicon membranes for different sample preparation routines and crystal orientations.
Using a large position-sensitive detector (0.13 sr), a depth resolution below 6 nm and sensitivity below 1014 atoms/cm2 was achieved for H in a 50 nm thick silicon membrane. For crystalline targets, we show how the probability of creation and detection of recoils and their observed angular distribution depend on sample orientation.

Keywords: Recoils; keV ions; Self-supporting films; Time-of-flight

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Permalink: https://www.hzdr.de/publications/Publ-35302
Publ.-Id: 35302


Tuning Iron-Oxygen Covalency in Perovskite Oxides for Efficient Electrochemical Sensing

Gao, C.; Lu, Y.; Wang, Y.; Wang, C.; Hübner, R.; Li, Y.; Zhan, J.; Zhao, M.; Cai, B.

Transition metal oxides have been extensively explored as novel catalysts for designing electrochemical sensors, but the underlying structure-activity relationship remains poorly understood. Herein, we explore a diverse chemical range of La1-xSrxFeO3 perovskite oxides by evaluating their electrochemical sensing activity toward heavy metals and by determining their electronic structures using density functional theory. We find that tuning perovskite chemistry plays an important role in determining the electrochemical activities and sensitivities, as well as the valence states of Fe. By combining experimental and theoretical analyses, a linear relationship between the Fe−O covalency and the electrochemical activity and sensitivity has been obtained, where LaFeO3 exhibits the highest activity of 109 mA cmoxide -2.Thus, the Fe−O covalency is proposed as a rational activity descriptor for the electrochemical sensing of heavy metals. A novel solid-state gelation method was further developed for the fabrication of perovskite oxide aerogels, based on which a highly efficient electrochemical sensor was constructed with a high sensitivity of 87.06 μM μA-1 and a low detection limit of 1.7 nM. This work unlocks an effective parameter, that is, Fe−O covalency, for rationally designing Fe-based oxides and deepening the understanding of fundamental parameters to develop highly efficient sensing platforms.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-35301
Publ.-Id: 35301


Towards a Seamlessly Interlinked Research Data and Software Ecosystem at HZDR

Knodel, O.

The talk gives insights into automated data and software publications. In this context, the HMC projects HELIPORT and HERMES are introduced and our path to a seamlessly interlinked research data and software ecosystem at the HZDR is shown.

Keywords: data management; data publication; software publication; HERMES; HELIPORT; workflows

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    2nd Helmholtz Open Science Practice Forum Research Data Management, 20.10.2022, online, Germany

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Permalink: https://www.hzdr.de/publications/Publ-35300
Publ.-Id: 35300


Chemical Vapor Deposition of High-Optical-Quality Large-Area Monolayer Janus Transition Metal Dichalcogenides

Gan, Z.; Paradisanos, I.; Estrada-Real, A.; Picker, J.; Najafidehaghani, E.; Davies, F.; Neumann, C.; Robert, C.; Wiecha, P.; Watanabe, K.; Taniguchi, T.; Marie, X.; Biskupek, J.; Mundszinger, M.; Leiter, R.; Krasheninnikov, A.; Urbaszek, B.; George, A.; Turchanin, A.

One-pot chemical vapor deposition (CVD) growth of large-area Janus SeMoS monolayers is reported, with the asymmetric top (Se) and bottom (S) chalcogen atomic planes with respect to the central transition metal (Mo) atoms. The for- mation of these !D semiconductor monolayers takes place upon the thermo- dynamic-equilibrium-driven exchange of the bottom Se atoms of the initially grown MoSe! single crystals on gold foils with S atoms. The growth process is characterized by complementary experimental techniques including Raman and X-ray photoelectron spectroscopy, transmission electron microscopy, and the growth mechanisms are rationalized by first principle calculations. The remark- ably high optical quality of the synthesized Janus monolayers is demonstrated by optical and magneto-optical measurements which reveal the strong exciton– phonon coupling and enable an exciton g-factor of −3.3.

Keywords: 2D materials; first-principles simulations; Janus heterostructures

Related publications

Permalink: https://www.hzdr.de/publications/Publ-35299
Publ.-Id: 35299


Refined Chelator Spacer Moieties Ameliorate the Pharmacokinetics of PSMA-617.

Dos, S. J.; Schäfer, M.; Bauder-Wüst, U.; Beijer, B.; Eder, M.; Leotta, K.; Kleist, C.; Meyer, J.; Dilling, T.; Lewis, J.; Kratochwil, C.; Kopka, K.; Haberkorn, U.; Mier, W.

Prostate-specific membrane antigen (PSMA) binding tracers are promising agents for the targeting of prostate tumors. To further optimize the clinically established radiopharmaceutical PSMA-617, novel PSMA ligands for prostate cancer endoradiotherapy were developed. A series of PSMA binding tracers that comprise a benzyl group at the chelator moiety were obtained by solid-phase synthesis. The compounds were labeled with 68Ga or 177Lu. Competitive cell-binding assays and internalization assays were performed using the cell line C4-2, a subline of the PSMA positive cell line LNCaP (human lymph node carcinoma of the prostate). Positron emission tomography (PET) imaging and biodistribution studies were conducted in a C4-2 tumor bearing BALB/c nu/nu mouse model. All 68Ga-labeled ligands were stable in human serum over 2 h; 177Lu-CA030 was stable over 72 h. The PSMA ligands revealed inhibition potencies [Ki] (equilibrium inhibition constants) between 4.8 and 33.8 nM. The percentage of internalization of the injected activity/10^6 cells of 68Ga-CA028, 68Ga-CA029, and 68Ga-CA030 was 41.2 ± 2.7, 44.3 ± 3.9, and 53.8 ± 5.4, respectively; for the comparator 68Ga-PSMA-617, 15.5 ± 3.1 was determined. Small animal PET imaging of the compounds showed a high tumor-to-background contrast. Organ distribution studies revealed high specific uptake in the tumor, that is, approximately 34.4 ± 9.8% of injected dose per gram (%ID/g) at 1 h post injection for 68Ga-CA028. At 1 h p.i., 68Ga-CA028 and 68Ga-CA030 demonstrated lower kidney uptake than 68Ga-PSMA-617, but at later time points, kidney time-activity curves converge. In line with the preclinical data, first diagnostic PET imaging using 68Ga-CA028 and 68Ga-CA030 revealed high-contrast detection of bone and lymph node lesions in patients with metastatic prostate cancer. The novel PSMA ligands, in particular CA028 and CA030, are promising agents for targeting PSMA-positive tumor lesions as shown in the preclinical evaluation and in a first patient, respectively. Thus, clinical translation of 68Ga-CA028 and 68Ga/177Lu-CA030 for diagnostics and endoradiotherapy of prostate cancer in larger cohorts of patients is warranted.

Keywords: PET imaging; PSMA; chelator; endoradiotherapy; prostate cancer

Permalink: https://www.hzdr.de/publications/Publ-35298
Publ.-Id: 35298


Ab initio study of shock-compressed copper

Schörner, M.; Witte, B. B. L.; Baczewski, A. D.; Cangi, A.; Redmer, R.

We investigate shock-compressed copper in the warm dense matter regime by means of density functional theory molecular dynamics simulations. We use neural-network-driven interatomic potentials to increase the size of the simulation box and extract thermodynamic properties in the hydrodynamic limit. We show the agreement of our simulation results with experimental data for solid copper at ambient conditions and liquid copper near the melting point under ambient pressure. Furthermore, a thorough analysis of the dynamic ion-ion structure factor in shock-compressed copper is performed and the adiabatic speed of sound is extracted and compared with experimental data.

Keywords: Condensed Matter Physics; Plasma Physics; Electronic Structure Theory; Density Functional Theory

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Permalink: https://www.hzdr.de/publications/Publ-35297
Publ.-Id: 35297


Data publication: Finite-element dynamic-matrix approach for propagating spin waves: Extension to mono- and multilayers of arbitrary spacing and thickness

Körber, L.; Hempel, A.; Otto, A.; Gallardo, R. A.; Henry, Y.; Lindner, J.; Kakay, A.

This dataset contains the numerically calculated data for our publication "Finite-element dynamic-matrix approach for propagating spin waves: Extension to mono- and multilayers of arbitrary spacing and thickness" published in AIP Advances. The data is structured as folders associated with each Figure showing any data. For cases in which different methods are compared, the data is separated into additional subfolders associated with each method (same naming scheme as in manuscript).

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-35296
Publ.-Id: 35296


Finite-element dynamic-matrix approach for propagating spin waves: Extension to mono- and multilayers of arbitrary spacing and thickness

Körber, L.; Hempel, A.; Otto, A.; Gallardo, R. A.; Henry, Y.; Lindner, J.; Kakay, A.

In our recent work [L. Körber, AIP Advances 11, 095006 (2021)], we presented an efficient numerical method to compute dispersions and mode profiles of spin waves in waveguides with translationally invariant equilibrium magnetization. A finite-element method (FEM) allowed to model two-dimensional waveguide cross sections of arbitrary shape but only finite size. Here, we extend our FEM propagating-wave dynamic-matrix approach from finite waveguides to the important cases of infinitely-extended mono- and multilayers of arbitrary spacing and thickness. To obtain the mode profiles and frequencies, the linearized equation of motion of magnetization is solved as an eigenvalue problem on a one-dimensional line-trace mesh, defined along the normal direction of the layers. Being an important contribution in multilayer systems, we introduce interlayer exchange into our FEM approach. With the calculation of dipolar fields being the main focus, we also extend the previously presented plane-wave Fredkin-Koehler method to calculate the dipolar potential of spin waves in infinite layers. The major benefit of this method is that it avoids the discretization of any non-magnetic material like non-magnetic spacers in multilayers. Therefore, the computational effort becomes independent on the spacer thicknesses. Furthermore, it keeps the resulting eigenvalue problem sparse, which therefore, inherits a comparably low arithmetic complexity. As a validation of our method (implemented into the open-source finite-element micromagnetic package \textsc{TetraX}), we present results for various systems and compare them with theoretical predictions and with established finite-difference methods. We believe this method offers an efficient and versatile tool to calculate spin-wave dispersions in layered magnetic systems.

Permalink: https://www.hzdr.de/publications/Publ-35295
Publ.-Id: 35295


The effects of post-processing on the local fracture toughness properties of electron beam powder bed fusion Ti-6Al-4V alloy

Dzugan, J.; Seifi, M.; Rzepa, S.; Rund, M.; Koukolikova, M.; Viehrig, H.-W.; Liu, Z. H.; Lewandowski, J. J.

Rapidly developing additive technologies for metallic parts production have led to the development of a wide range of methods supporting this field, including mechanical properties characterization. Components produced by AM processes are built spot to spot and layer by layer and that leads to varying local heat absorption and distribution, resulting in varying local properties depending on the shape complexity and build parameters. Different properties in different directions and at various component locations can be expected. Since AM parts are often sub-scale and/or with topological complexity, mechanical characterization with the use of standard specimens is not typically possible and small-sized specimen techniques have to be developed and applied. In the current paper, three AM produced parts made of Ti-6Al-4V by Electron Beam Powder Bed Fusion (EB-PBF) technology have been investigated. Three material conditions are reported here: as-deposited, stress relieved and HIP-ed. Local mechanical properties are assessed with the use of miniaturized compact tension (MCT) fracture toughness specimens and miniaturized tensile tests (MTT). The results are complemented by microstructural and fractographic analysis and are discussed in the light of literature values. © 2022 Elsevier Ltd

Keywords: Additive manufacturing; Fracture toughness; Local properties; Miniature tension and fracture toughness specimens

Permalink: https://www.hzdr.de/publications/Publ-35294
Publ.-Id: 35294


Low-energy ion channeling in nanocubes

Choupanian, S.; Möller, W.; Seyring, M.; Ronning, C.

Focused ion beam (FIB) processing with low-energy ions has become a standard technique for the manipulation of nanostructures. Many underlying ion beam effects that deviate from conventional high-energy ion irradiation of bulk systems are considered today; however, ion channeling with its consequence of significant deeper penetration depth has been only theoretically investigated in this regime. We present here an experimental approach to determine the channeling of low-energy ions in crystalline nanoparticles by measuring the sputter yield derived from scanning electron microscopy (SEM) images taken after irradiation under various incident ion angles. Channeling maps of 30 and 20 keV Ga+ ions in Ag nanocubes have been identified and fit well with the theory. Indeed, channeling has a significant impact on the transport of energetic ions in crystals due to the large critical angle at low ion energies, thus being relevant for any FIB-application. Consequently, the obtained sputter yield clearly differs from amorphous materials; therefore, it is recommended not to rely only on, e.g., ion distribution depths predicted by standard Monte-Carlo (MC) algorithms for amorphous materials.

Keywords: focused ion beam; ion channeling; ion nanostructure interaction; metallic nanoparticles

Related publications

Permalink: https://www.hzdr.de/publications/Publ-35293
Publ.-Id: 35293


Highlight selection of radiochemistry and radiopharmacy developments by editorial board.

Toyohara, J.; Al-Qahtani, M.; Huang, Y.; Cazzola, E.; Todde, S.; Furumoto, S.; Mikolajczak, R.; Decristoforo, C.; Gillings, N.; Yang, M.; Reilly, R.; Duatti, A.; Denkova, A.; Schirrmacher, R.; Carlucci, G.; Seimbille, Y.; Liu, Z.; Ellis, B.; Cornelissen, B.; Kopka, K.; Bernardes, E.

Background: The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biannual highlight commentary to update the readership on trends in the field of radiopharmaceutical development.
Main body: This commentary of highlights has resulted in 21 different topics selected by each coauthoring Editorial Board member addressing a variety of aspects ranging from novel radiochemistry to first in man application of novel radiopharmaceuticals.
Conclusion: Trends in radiochemistry and radiopharmacy are highlighted demonstrating the progress in the research field in various topics including new PET-labelling methods, FAPI-tracers and imaging, and radionuclide therapy being the scope of EJNMMI Radiopharmacy and Chemistry.

Keywords: Highlight Articles; Nuclear Medicine; Radiochemistry; Radiopharmaceutical Sciences; Radiopharmacy; Trends in Radiopharmaceutical Sciences

Permalink: https://www.hzdr.de/publications/Publ-35288
Publ.-Id: 35288


Stimulated Resonant Inelastic X-Ray Scattering in a Solid

Higley, D. J.; Chen, Z.; Beye, M.; Hantschmann, M.; Reid, A. H.; Mehta, V.; Hellwig, O.; Dakovski, G. L.; Mitra, A.; Engel, R. Y.; Maxwell, T.; Ding, Y.; Bonetti, S.; Bucher, M.; Carron, S.; Chase, T.; Jal, E.; Kukreja, R.; Liu, T.; Föhlisch, A.; Dürr, H. A.; Schlotter, W. F.; Stöhr, J.

When materials are exposed to X-ray pulses with sufficiently high intensity, various nonlinear
effects can occur. The most fundamental one consists of stimulated electronic decays after
resonant absorption of X-rays. Such stimulated decays enhance the number of emitted
photons and the emission direction is confined to that of the stimulating incident photons
which clone themselves in the process. Here we report the observation of stimulated reso-
nant elastic (REXS) and inelastic (RIXS) X-ray scattering near the cobalt L3 edge in solid Co/
Pd multilayer samples. We observe an enhancement of order 106 of the stimulated over the
conventional spontaneous RIXS signal into the small acceptance angle of the RIXS spectro-
meter. We also find that in solids both stimulated REXS and RIXS spectra contain con-
tributions from inelastic electron scattering processes, even for ultrashort 5 fs pulses.
Our results reveal the potential and caveats of the development of stimulated RIXS in
condensed matter.

Permalink: https://www.hzdr.de/publications/Publ-35287
Publ.-Id: 35287


Cooperative Effect of Electron Spin Polarization in Chiral Molecules Studied with Non-Spin-Polarized Scanning Tunneling Microscopy

Ngoc Ha Nguyen, T.; Rasabathina, L.; Hellwig, O.; Sharma, A.; Salvan, G.; Yochelis, S.; Paltiel, Y.; Baczewski, L. T.; Tegenkamp, C.

Polyalanine molecules (PA) with an α-helix conformation have
recently attracted a great deal of interest, as the propagation of electrons through the
chiral backbone structure comes along with spin polarization of the transmitted
electrons. By means of scanning tunneling microscopy and spectroscopy under
ambient conditions, PA molecules adsorbed on surfaces of epitaxial magnetic Al2O3/
Pt/Au/Co/Au nanostructures with perpendicular anisotropy were studied. Thereby,
a correlation between the PA molecules ordering at the surface with the electron
tunneling across this hybrid system as a function of the substrate magnetization
orientation as well as the coverage density and helicity of the PA molecules was
observed. The highest spin polarization values, P, were found for well-ordered self-
assembled monolayers and with a defined chemical coupling of the molecules to the
magnetic substrate surface, showing that the current-induced spin selectivity is a
cooperative effect. Thereby, P deduced from the electron transmission along
unoccupied molecular orbitals of the chiral molecules is larger as compared to values
derived from the occupied molecular orbitals. Apparently, the larger orbital overlap results in a higher electron mobility, yielding a
higher P value. By switching the magnetization direction of the Co layer, it was demonstrated that the non-spin-polarized STM can
be used to study chiral molecules with a submolecular resolution, to detect properties of buried magnetic layers and to detect the
spin polarization of the molecules from the change in the magnetoresistance of such hybrid structures.

Permalink: https://www.hzdr.de/publications/Publ-35286
Publ.-Id: 35286


Role of vibrational properties and electron-phonon coupling on thermal transport across metal-dielectric interfaces with ultrathin metallic interlayers

Mary Oommen, S.; Fallarino, L.; Heinze, J.; Hellwig, O.; Pisana, S.

We systematically analyze the influence of 5 nm thick metal interlayers inserted at the interface
of several sets of different metal-dielectric systems to determine the parameters that most
influence interface transport. Our results show that despite the similar Debye temperatures of
Al2O3 and AlN substrates, the thermal boundary conductance measured for the Au/Al2O3
system with Ni and Cr interlayers is ∼2× and >3× higher than the corresponding Au/AlN
system, respectively. We also show that for crystalline SiO2 (quartz) and Al2O3 substrates
having highly dissimilar Debye temperature, the measured thermal boundary conductance
between Al/Al2O3 and Al/SiO2 are similar in the presence of Ni and Cr interlayers. We suggest
that comparing the maximum phonon frequency of the acoustic branches is a better parameter
than the Debye temperature to predict the change in the thermal boundary conductance. We
show that the electron–phonon coupling of the metallic interlayers also alters the heat transport
pathways in a metal-dielectric system in a nontrivial way. Typically, interlayers with large
electron–phonon coupling strength can increase the thermal boundary conductance by dragging
electrons and phonons into equilibrium quickly. However, our results show that a Ta interlayer,
having a high electron–phonon coupling, shows a low thermal boundary conductance due to the
poor phonon frequency overlap with the top Al layer. Our experimental work can be interpreted
in the context of diffuse mismatch theory and can guide the selection of materials for thermal
interface engineering.

Keywords: hermal boundary conductance; metal-dielectric interfaces; Debye temperature; phonon frequencies; time-domain thermoreflectance

Permalink: https://www.hzdr.de/publications/Publ-35285
Publ.-Id: 35285


Tailoring exchange-dominated synthetic layered antiferromagnets: From collective reversal to exchange bias

Benny, B.; Hellwig, O.

Not only since the progressive reduction of structure sizes in modern micro- and nanotechnology, surface and interface effects have played an ever-increasing role and nowadays often dominate the behavior of entire systems. Therefore, understanding the nature of surface and interface effects and being able to fully control them is of fundamental importance, in particular in modern thin-film technology. In this study, it is revealed how Co/Pt multi-layer-based synthetic antiferromagnets (SAFs) with perpendicular magnetic anisotropy in the regime of dominating antiferromagnetic interlayer exchange can be employed to control the collective magnetic reversal via systemati-cally altering surface and interface effects. The specifically designed samples and experiments highlight the superior tunability of synthetic systems as compared to their intrinsic stoichiometric counterparts, where the antiferro-magnetism is directly tied to the indivisible discrete atomic nature and crystal structure of the materials. Thus, it is demonstrated that in SAFs, it becomes possible to energetically heal the broken magnetic symmetry at the surface, thereby enabling either on demand suppression or controlled enhancement of respective surface and interface effects, as demonstrated here in this study for the surface spin-flop and the exchange bias effect.

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Permalink: https://www.hzdr.de/publications/Publ-35284
Publ.-Id: 35284


Temperature dependent intercalation of molten 1-hexadecanol into Brodie graphite oxide

Nordenström, A.; Iakunkov, A.; Boulanger, N.; Li, G.; Hennig, C.; Baburin, I.; Jørgensen, M.; Kantor, I.; Talyzin, A. V.

Intercalation of very long molecules into the structure of multi-layered graphene oxide was studied using example of 1-hexadecanol (C16), an alcohol molecule with 16 carbon atoms and length of about 22Å. Brodie graphite oxide (BGO) immersed in excess of liquid 1-hexadecanol just above the melting point shows expansion of c-unit cell parameter from ~6Å to ~48.76 Å forming a structure with two densely packed layers of C16 molecules in a vertical “stand up” orientation relative to graphene oxide planes (α-phase). Heating of the BGO-C16 α-phase in excess of C16 melt results in reversible phase transition into β-phase at 336-342K. The β-phase shows much smaller c-unit cell of 29.83 Å (363K). Analysis of data obtained using vacuum-driven evaporation of C16 from the β-phase and set of experiments with samples pre-mixed with different BGO:C16 proportions provides evidence for structure of β-phase consisting of five layers of C16 molecules in parallel to GO plane orientation. Therefore, the transition from α- to β- phase corresponds to change in orientation C16 molecules from vertical to parallel to GO planes and significant decrease in amount of intercalated solvent. Cooling of β-phase in absence of C16 melt is found to result in the formation of γ-phase with interlayer distance of ~26.5Å. This distance corresponds to one layer of C16 molecules intercalated in vertical relative to GO planes orientation. Finally, structures with one and two layers of C16 molecules parallel to GO planes were identified in samples with rather small initial loading of C16. Surprisingly rich variety of structures revealed in BGO-C16 system provides opportunities to create materials with precisely controlled GO inter-layer distance.

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Permalink: https://www.hzdr.de/publications/Publ-35283
Publ.-Id: 35283


Single- and Multilayers of Alkali Metal Atoms Inside Graphene/MoS2 Heterostructures: a Systematic First-Principles Study

Chepkasov, I. V.; Smet, J. H.; Krasheninnikov, A.

Stacking various two-dimensional (2D) materials in van der Waals (vdW) het- erostructures is a novel approach to design new systems, which can host alkali metal (AM) atoms to tune their electronic properties or store energy. Using state-of-the-art first-principles calculations, we systematically study the intercalation of the most wide- spread AMs (Li, Na, K) into a graphene/MoS2 heterostructure. Contrary to previous work on the intercalation of AMs into various heterostructures based on 2D materials, we consider not only single-, but also multi-layer configurations of AM atoms. We assess the intercalation energetics for various concentrations of AM atoms, calculate charge transfer from AM atoms to the host system, and show that although interca- lation of AMs as single layer is energetically preferable, multi-layer configurations can exist at high concentrations of AM atoms. We further demonstrate that the transition of the MoS2 layer from the H to T ′ phase is possible upon Li intercalation, but not Na or K. Our findings should help to better understand the behavior of heterostructures upon AM atom intercalation and may stimulate further experiments aimed at the tai- loring of heterostructure properties and increasing the capacity of anode materials in AM ion batteries.

Keywords: Graphene/MoS2 Heterostructures; Li ions; intercalation; first-principles calculations

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  • Secondary publication expected from 07.09.2023

Permalink: https://www.hzdr.de/publications/Publ-35281
Publ.-Id: 35281


Atomistic Simulations of Defects Production under Ion Irradiation in Epitaxial Graphene on SiC

Jain, M.; Kretschmer, S.; Höflich, K.; Lopes, J. M. J.; Krasheninnikov, A.

Using first-principles and analytical potential atomistic simulations, we study the production of defects in epitaxial graphene on SiC upon ion irradiation for ion types and energies accessible in helium ion microscope. We focus on graphene-SiC systems consisting of the buffer (zero) graphene layer and SiC substrate, as well as one (monolayer) and two (bilayer) additional graphene layers. We calculate the probabilities for single, double and more complex vacancies to appear upon impacts of energetic ions in each graphene layer as functions of He and Ne ion energies, and compare the data to those obtained for the free standing graphene. The results indicate that the role of substrate is minimal for He-ion irradiation with energies above 5 keV, which can be associated with a low sputtering yield from this system upon ion irradiation, as compared to common Si/SiO2 substrate. In contrast, SiC substrate has a significant effect on defect production upon Ne-ion irradiation. Our results can serve as a guide to the experiments on ion irradiation of epitaxial graphene to choose the optimum ion beam parameters for defect-mediated engineering of such systems, e.g., for creating nucleation centers to grow other two-dimensional materials, such as h-BN, on top of the irradiated epitaxial graphene.

Keywords: graphene; irradiation; defects; atomsitic simulations

Related publications

Permalink: https://www.hzdr.de/publications/Publ-35280
Publ.-Id: 35280


Influence of Pretreatment Strategy on the Crushing of Spent Lithium-Ion Batteries

Werner, D.; Mütze, T.; Peuker, U.

The rising production of lithium-ion batteries (LIBs) due to the introduction of electric mobility as well as stationary energy storage devices demands an efficient and sustainable waste man-agement scheme for legislative, economic and ecologic reasons. One crucial part of the recycling of end-of-life (EOL) LIBs is mechanical processes, which generate material fractions for the pro-duction of new batteries or further metallurgical refining. In the context of safe and efficient processing of electric vehicles’ LIBs, crushing is usually applied as a first process step to open at least the battery cell and liberate the cell components. However, the cell opening method used requires a specific pretreatment to overcome the LIB’s hazard potentials. Therefore, the depend-ence on pretreatment and crushing is investigated in this contribution. For this, the energy input for liberation is determined and compared for different recycling strategies with respect to dis-mantling depth and depollution temperatures. Furthermore, the respective crushing product is analyzed regarding granulometric properties, material composition and liberation and decoat-ing behaviour depending on the pretreatment and grid size of the crushing equipment. Finer particles and components are generated with dried cells. Pyrolysis of cells, as well as high dis-mantling depths, do not allow to draw exact conclusions. The calculated and measured mass-specific mechanical energy input of different dismantling depths shows good accuracy. Consequently, trends for a successful separation strategy of the subsequent classifying and sort-ing processes are revealed, and recommendations for the liberation of LIBs are derived.

Keywords: lithium-ion battery; recycling; EV batteries; battery cells; processing; crushing; waste management; circular economy

Permalink: https://www.hzdr.de/publications/Publ-35279
Publ.-Id: 35279


Proton acceleration at DRACO-PW surpassing the 100 MeV frontier

Ziegler, T.; Peter Dover, N.; Assenbaum, S.; Garten, M.; Gaus, L.; Göthel, I.; Kluge, T.; Kroll, F.; Nishiuchi, M.; Reimold, M.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Schramm, U.; Zeil, K.

Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power laser driven compact plasma accelerators enable generation of short, high-intensity pulses of high energy ions with special beam properties. These accelerators promise to expand the portfolio of conventional machines in many application areas. The maturation of laser driven ion accelerators from physics experiments to turn-key sources for these applications will rely on breakthroughs in both, generated beam parameters (kinetic energy, flux), as well as increased scrutiny on reproducibility, robustness and scalability to high repetition rate.
Recent developments at the high-power laser facility DRACO-PW enabled the production of polychromatic proton beams with unprecedented stability [1]. This allowed the first in vivo radiobiological study to be conducted using a laser-driven proton source [2]. Yet, the ability to achieve energies beyond the 100 MeV frontier is essential for many applications and a matter of ongoing research, mainly addressed by exploring advanced acceleration schemes like the relativistically induced transparency regime.
In this talk we report on experimental proton acceleration studies at the onset of relativistic transparency using linearly polarized laser pulses with peak intensities of 6x21 W/cm2 focused on thin, pre-expanded plastic foils. Combined hydrodynamic and 3D particle-in-cell simulations helped to identify the most promising target parameter range matched to the carefully measured prevailing laser contrast conditions. In a nutshell, the ultra-intense femtosecond pulse interaction induces large accelerating gradients and energy gain dominantly arising from significant space charge fields due to electron expulsion from the relativistic transparent target core followed by weaker post-acceleration in diffuse sheath fields at later times. A complex suite of particle and optical diagnostics allowed characterization of spatial and spectral proton beam parameters and the stability of the regime of best acceleration performance, yielding cut-off energies larger than 100 MeV in the best shots.

  • Lecture (Conference)
    8th annual "Matter and Technologies" meeting, 26.-27.09.2022, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35278
Publ.-Id: 35278


Proton acceleration in the relativistically induced transparency regime at DRACO-PW surpassing the 100 MeV frontier

Ziegler, T.; Peter Dover, N.; Assenbaum, S.; Garten, M.; Gaus, L.; Göthel, I.; Kluge, T.; Kroll, F.; Nishiuchi, M.; Reimold, M.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Schramm, U.; Zeil, K.

Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power laser driven compact plasma accelerators enable generation of short, high-intensity pulses of high energy ions with special beam properties. These accelerators promise to expand the portfolio of conventional machines in many application areas. The maturation of laser driven ion accelerators from physics experiments to turn-key sources for these applications will rely on breakthroughs in both, generated beam parameters (kinetic energy, flux), as well as increased scrutiny on reproducibility, robustness and scalability to high repetition rate.
Recent developments at the high-power laser facility DRACO-PW enabled the production of polychromatic proton beams with unprecedented stability [1]. This allowed the first in vivo radiobiological study to be conducted using a laser-driven proton source [2]. Yet, the ability to achieve energies beyond the 100 MeV frontier is essential for many applications and a matter of ongoing research, mainly addressed by exploring advanced acceleration schemes like the relativistically induced transparency regime.
In this talk we report on experimental proton acceleration studies at the onset of relativistic transparency using linearly polarized laser pulses with peak intensities of 6x21 W/cm2 focused on thin, pre-expanded plastic foils. Combined hydrodynamic and 3D particle-in-cell simulations helped to identify the most promising target parameter range matched to the carefully measured prevailing laser contrast conditions. In a nutshell, the ultra-intense femtosecond pulse interaction induces large accelerating gradients and energy gain dominantly arising from significant space charge fields due to electron expulsion from the relativistic transparent target core followed by weaker post-acceleration in diffuse sheath fields at later times. A complex suite of particle and optical diagnostics allowed characterization of spatial and spectral proton beam parameters and the stability of the regime of best acceleration performance, yielding cut-off energies larger than 100 MeV in the best shots.

  • Lecture (Conference)
    9th International Conference on Ultrahigh Intensity Lasers, 19.-23.09.2022, Jeju Island, Südkorea

Permalink: https://www.hzdr.de/publications/Publ-35277
Publ.-Id: 35277


High-temperature sensible thermal energy storage (STES) Thermo-economic assessment for various designs, storage materials and heat transfer fluids

Bangalore Mohankumar, M.; Unger, S.; Hampel, U.

An energy storage (ES) system is an economical and reliable technology that plays a
predominant role in making the renewable energy sector sustainable. Integration of ES with
wind and solar plants provides solution to problem of grid instability caused by to fluctuating
power output. The Thermal Energy Storage (TES) system is simple and has low environmental
and social impacts compared to other ES technologies like batteries, pumped hydro,
compressed air and chemical storage. However, application of a TES at high temperature is
quite unexplored and has a limited deployment globally.
Solid sensible TES (STES) stores excess electricity in form of sensible heat, the solid medium
is directly electrical heated or indirectly heated using heat transfer fluids (HTF). In STES
systems, no phase change nor chemical reactions involved. Hence, it is simple, easy to
maintain and the cost of construction materials is low. The foresaid advantages makes it
suitable for high temperature applications provided the solid material selected exhibits higher
temperature stability.
The poster will highlight the thermal performance of STES for 10 MWth power output over 24
hours, resulting in a storage capacity of 240 MWhth at high temperature of 800 °C. The
candidates of investigation are most commonly used solid materials, like high temperature
ceramic, high temperature concrete, firebricks, alferrock as well as vitrified flyash and as HTFs
Air, He, CO2 and N2 were studied. The influence of geometry, flow rate, heat transfer surface
area and solid material configuration in storage tank on the thermodynamics of TES system
cannot be ignored. Therefore, different STES designs were also included for assessment in
this research work.
To investigate the thermal performance of a STES system in terms of all the above-mentioned
candidates, a One-dimensional model will be developed in MATLAB and validated with data
available in literature. Based on results, the performance parameters like solid temperature
during charging/discharging cycle as well as overall thermal efficiency are evaluated. In addition, the economical assessment of different TES designs and materials can be estimated in €/MWhth.

  • Open Access Logo Poster
    54th Kraftwerkstechnisches Kolloquium, 18.-19.10.2022, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-35275
Publ.-Id: 35275


Fluid Dynamics of Na-Zn Liquid Metal Batteries

Weber, N.

The talk will start with an overview on the working principle of the all-liquid Na-Zn molten salt battery. Thereafter, various fluid dynamic effects, which might appear in such cells, will be discussed.

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Open for Business event: Liquid Metal Batteries, 15.11.2022, Cambridge, United Kingdom

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Permalink: https://www.hzdr.de/publications/Publ-35274
Publ.-Id: 35274


Performance boost of a collective qutrit refrigerator

Kolisnyk, D.; Schaller, G.

A single qutrit with transitions selectively driven by weakly-coupled reservoirs can implement one of the world's smallest refrigerators. We analyze the performance of N such fridges that are collectively coupled to the reservoirs. We observe a quantum boost, manifest in a quadratic scaling of the steady-state cooling current with N. As N grows further, the scaling reduces to linear, since the transitions responsible for the quantum boost become energetically unfavorable. Fine-tuned inter-qutrit interactions may be used to maintain the quantum boost for all N and also for not-perfectly collective scenarios.

Keywords: open quantum systems; Lindblad equation; Redfield equation; collective effects; quantum absorption refrigerator; qutrits; Holstein-Primakoff transform; quadratic boost; nonequilibrium steady state

Permalink: https://www.hzdr.de/publications/Publ-35273
Publ.-Id: 35273


Flexible and printable magnetoelectronics for human-machine interfaces and soft robotics

Makarov, D.

Motion sensing is the primary task in numerous disciplines including industrial robotics, prosthetics, virtual and augmented reality appliances. In rigid electronics, rotations, displacements and vibrations are typically monitored using magnetic field sensors. Here, we will discuss the fabrication of flexible, stretchable and printable magnetoelectronic devices. The technology platform relies on high-performance magnetoresistive and Hall effect sensors deposited or printed on ultrathin polymeric foils. These skin conformal flexible and printable magnetosensitive elements enable touchless interactivity with our surroundings based on the interaction with magnetic fields, which is relevant for smart skins, soft robotics and human-machine interfaces.

Keywords: flexible magnetic field sensors; printable magnetic field sensors; magnetic soft robots; magnetic field sensors

Related publications

  • Lecture (others)
    PhD workshop of the Institute of Physical Chemistry and Physics of Polymers (Institute Director Prof. Dr. Andreas Fery), 14.10.2022, Struppen/OT Naundorf, Germany

Permalink: https://www.hzdr.de/publications/Publ-35271
Publ.-Id: 35271


Examining different regimes of ionization-induced damage in GaN through atomistic simulations

Sequeira, M.; Djurabekova, F.; Nordlund, K.; Mattei, J.-G.; Monnet, I.; Grygiel, C.; Alves, E.; Lorenz, K.

The widespread adoption of gallium nitride (GaN) in radiation-hard semiconductor devices relies on a comprehensive understanding of its response to strongly ionizing radiation. Despite being widely acclaimed for its high radiation resistance, the exact effects induced by ionization are still hard to predict due to the complex phase-transition diagrams and defect creation-annihilation dynamics associated with group-III nitrides. Here, Two-Temperature Model, Molecular Dynamics simulations and Transmission Electron Microscopy, are employed to study the interaction of Swift Heavy Ions with GaN at the atomic level. The simulations reveal a high propensity of GaN to recrystallize the region melted by the impinging ion leading to high thresholds for permanent track formation. Although the effect exists in all studied electronic energy loss regimes, its efficiency is reduced with increasing electronic energy loss, in particular when there is dissociation of the material and subsequent formation of N 2 bubbles. The recrystallization is also hampered near the surface where voids and pits are prominent. The exceptional agreement between the simulated and experimental results establishes the applicability of the model to examine the entire electronic energy loss spectrum. Furthermore, the model supports an empirical relation between the interaction cross sections (namely for melting and amorphization) and the electronic energy loss.

Keywords: Defects; GaN; Molecular Dynamics; Radiation; Recrystallization

Permalink: https://www.hzdr.de/publications/Publ-35270
Publ.-Id: 35270


Personnel staffing and scheduling during disease outbreaks: A contact network-based analysis

Batista German, A. C.; Senapati, A.; Davoodi Monfared, M.; Calabrese, J.

Personnel scheduling in organizations can be disrupted by unforeseen events that require efficient planning. A recent example is the COVID-19 pandemic that disrupted global operations, compromising people's health and safety. Many organizations were forced to transition to full remote work to prevent the spread of the virus and ensure employee safety. Although working entirely remotely is effective for some organizations, others must balance workplace occupancy and infection risk to keep their operations functioning efficiently despite a global health crisis. We address this issue by developing a days-off scheduling model that captures employees' interactions through the underlying contact network. To solve the problem, we propose a Mixed Integer Linear Programming model considering a Microscopic Markov Chain Approach to determine the probability of infection in a contact network that mimics the employees' interactions. The model determines, during a given planning period, the optimal staffing mix to maximize occupancy while minimizing the risk of infection in the presence of testing protocols. We conduct sensitivity analysis to assess the approach's robustness while considering different contact networks and testing strategies. Through extensive computational analysis, we show that the degree of contact among employees is not the sole factor to consider when defining personnel scheduling policies during disease outbreaks. The decision-maker must balance the employee allocation with tailored testing interventions based on management's priorities to mitigate the effects while ensuring the desired occupancy at a lower risk.

Keywords: personnel scheduling; days-off scheduling; disease modeling; COVID-19

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Permalink: https://www.hzdr.de/publications/Publ-35268
Publ.-Id: 35268


Large-Scale Structure Prediction of Near-Stoichiometric Magnesium Oxide based on a Machine-Learned Interatomic Potential

Tahmasbi, H.; Goedecker, S.; Ghasemi, S. A.

Using a fast and accurate neural network potential, we are able to systematically
explore the energy landscape of large unit cells of bulk magnesium oxide with the
minima hopping method. The potential is trained with a focus on the near-
stoichiometric compositions, in particular on suboxides, i.e., Mg x O 1−x with 0.50 < x <
0.60. Our extensive exploration demonstrates that for bulk stoichiometric
compounds, there are several new low-energy rock-salt-like structures in which Mg
atoms are octahedrally six-coordinated and form trigonal prismatic motifs with
different stacking sequences.
Furthermore, we find a dense spectrum of novel nonstoichiometric crystal phases of
Mg x O 1−x for each composition of x. These structures are mostly similar to the rock-salt
structure with octahedral coordination and five-coordinated Mg atoms. Due to the
removal of one oxygen atom, the energy landscape becomes more glass-like with
oxygen-vacancy type structures that all lie very close to each other energetically. For
the same number of magnesium and oxygen atoms, our oxygen-deficient structures
are lower in energy if the vacancies are aligned along lines or planes than rock-salt
structures with randomly distributed oxygen vacancies. We also found the putative
global minima configurations for each composition of the nonstoichiometric suboxide
structures. These structures are predominantly composed of MgO(111) layers of the
rock-salt structure which are terminated with Mg atoms at the top and bottom and
are stacked in different sequences along the z direction. Like for other materials,
these Magnéli-type phases have properties that differ considerably from their
stoichiometric counterparts such as high electrical conductivity

  • Poster
    Strongly Coupled Coulomb Systems (SCCS) 2022 Conference, 24.07.2022, Goerlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-35266
Publ.-Id: 35266


Das Handy - Die Rohstoffquelle in Deiner Tasche; Rohstoffkreisläufe als wesentlicher Faktor im Klimaschutz

Möckel, R.

Rohstoffkreisläufe schließen als wesentlicher Faktor für den Klimaschutz - wo sind die Grenzen des Recyclings? Können wir bei hoher Recyclingquote auch auf Bergbau verzichten? Unsere Herausforderungen erklärt an den Beispielen des Handys und der Elektromobilität.

Keywords: Klima; Recycling; Circular Economy

  • Invited lecture (Conferences)
    Jugendklimakonferenz Chemnitz, 11.06.2022, Chemnitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35265
Publ.-Id: 35265


The mineralogy of GeoPT samples

Ebert, D.; Renno, A.; Möckel, R.

As has been stated e.g. in Meisel et al. (2022) that the mineralogical composition of a certain sample
does have an influence on the analytical geochemical results obtained. Prior to the start of the analytical
geochemical studies, an approximate idea of the mineralogical composition of the sample to be
analyzed should be available. This helps to select the digestion method and the methods to be used
(matrix effect).
We chose 14 samples from different GeoPT rounds representing a wide spectrum of rock composition
for a detailed quantitative X-ray diffraction (XRD) study.
Based on the determined quantitative mineralogical composition, an estimation of the chemical
composition can be made. This is achieved by a back calculation using the mineral chemistry of the
identified mineral phases. The Profex/BGMN software package (Doebelin & Kleeberg, 2015)
automatically calculates these values. These data can be directly compared with the results of a GeoPT
round robin.
It must be taken into account that the sample preparation for a GeoPT round robin is not ideal for
quantitative XRD investigations and artifacts must be expected. XRD slightly underestimates e.g.
SiO2-values (Fig. 1). This is mainly due to an overgrinding effect, where quartz forms an
“amorphization” layer at the surface (O’Connor & Chang, 1986).

Keywords: proficiency testing; mineralogy

  • Poster
    Geoanalysis 2022, 06.-12.08.2022, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35264
Publ.-Id: 35264


Mineralogical proficiency testing aligned with the GeoPT programme? Opportunities and challenges - an interactive poster

Möckel, R.; Webb, P. C.; Gowing, C. B.; Potts, P. J.; Renno, A.

The GeoPT programme (IAG, 2020) is a valuable tool that allows geochemical laboratories to test their routine analytical performance and, if necessary, undertake remedial action where errors of inappropriate magnitude are detected. During the past 25 years and 63 rounds so far, the GeoPT programme has provided a great variety of rock samples for the benefit of participants. While the GeoPT programme solely focuses on geochemical composition data, it is well known that the mineralogical content of geochemical materials is also of importance to analysts, to researchers and to industrialists (e.g. Meisel et al. 2022). It has long been known that the so-called mineralogical effect can influence the quantitative outcomes of XRF measurements made on pressed pellets. In addition, wet chemical techniques may also suffer from incomplete digestion when resistant minerals are present, unless a rigorous multi acid attack or a combination of fusion and dissolution are employed. The mineralogical content of geological materials is, therefore, important but is not implicitly assessed in the GeoPT programme. Is there a need, therefore, for a dedicated mineralogical proficiency testing programme (MinPT?)?

To our knowledge, there is only one regular mineralogical round robin interlaboratory test programme – the biennial Reynolds Cup (Raven & Self, 2017), which focuses on clay minerals and follows a slightly different approach as the composition of the material is known to the organizers at the outset.

The reason for this interactive poster is to investigate the need for a mineralogical interlaboratory round robin test linked to the GeoPT proficiency testing programme. The idea is that essentially the same material would be distributed in a simultaneous GeoPT and mineralogical test round. Special preparation procedures will be required to ensure that the test material is suitable for both geochemical and mineralogical laboratories operating techniques such as X-ray diffraction, automated mineralogy (MLA, QUEMSCAN, TIMA, etc.) and others. Quantitative mineralogical data from this round robin test would be assessed where possible, using the same well-established GeoPT procedures and providing participating laboratories with personalized performance data. Furthermore, a direct comparison with bulk compositional data from the complementary GeoPT round would permit further insights into analytical performance. It is important to note that there is no expectation that participating laboratories would have to participate in both the GeoPT and mineralogical rounds, but participation in both would be welcomed.

With the help of this interactive poster, we would like to ask delegates for indications of their general interest in participating in a combined mineralogical/geochemical test of proficiency based on effectively the same test materials.

References:

Meisel, T. C., Webb, P. C., & Rachetti, A. (2022). Highlights from 25 Years of the Geo PT Programme: What Can be Learnt for the Advancement of Geoanalysis. Geostandards and Geoanalytical Research.
Raven, M. D., & Self, P. G. (2017). Outcomes of 12 years of the Reynolds Cup quantitative mineral analysis round robin. Clays and Clay Minerals, 65(2), 122-134.
IAG (2020). Protocol for the operation of the GeoPT Proficiency testing scheme. International Association of Geoanalysts (Keyworth, UK), 18pp. http://www.geoanalyst.org/wp-content/uploads/2020/07/GeoPT-revised-protocol-2020.pdf.

Keywords: proficiency testing; mineralogy

  • Poster
    Geoanalysis 2022, 06.-12.08.2022, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35263
Publ.-Id: 35263


Das Handy - Die Rohstoffquelle in Deiner Tasche

Möckel, R.

Nachhaltiger Umgang mit natürlichen Rohstoffquellen ist eine der drängendsten Aufgaben unserer Gesellschaft. Das Konzept dazu ist die sogn. Kreislaufwirtschaft. Damit verbunden sind Worte wie Nachhaltigkeit und Recycling. Doch alles was recycled wird, muss erst durch Bergbau gewonnen werden. Wo sind die Grenzen des Recyclings? Können wir bei hoher Recyclingquote auch auf Bergbau verzichten?

Jeder von uns hat ein Handy und die Anzahl der Elektroautos nimmt zu. Dazu braucht man Rohstoffe, die zuvor in diesen Mengen nicht benötigt wurden. Die Herausforderungen für die Gewinnung der Rohstoffe werden an Beispielen des Handys und der Elektromobilität erklärt.

  • Lecture (others)
    DMG Köln 2022, 11.09.2022, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35262
Publ.-Id: 35262


Mineralogy and Processing experiments of an unusual parasite bearing REE ore from northern Vietnam

Möckel, R.; Gutzmer, J.; Burisch-Hassel, M.; Cardenas-Vera, A.; Hesse, M.; Heinig, T.; van Phang, Q.

The cabonatite-hosted Namxe rare earth element (REE) deposit in northern Vietnam has a total rare earth oxide (TREO) content of up to 2 wt% which is mainly hosted by parasite in the southern part of the deposit. Detailed mineralogical investigation of the rather complex mineralization revealed that parisite occurs in two geochemical varieties with slightly differing REE2O3/CaO ratios (5.8 ±0.2 vs. 6.8 ±0.35). Parisite occurs in dykes together with carbonates (ankerite, calcite) and barite and is often intergrown with fine-grained (sub 100µm size fraction) barite-celestine group minerals. The recognition of remnants of corroded bastnaesite suggest that REE enrichment is a result of a multi-stage process involving Sr- and CO3-rich fluids with mantle signature (δ13C values of -6.8 ‰ to -2.89 ‰) with no or little additional REE input.
We applied state-of-the-art techniques to propose a possible processing route of the ore, including experiments using sensor-sorting, selective comminution, magnetic separation (HIMS and WHIMS) and froth flotation. Sensor sorting turned out to be quite efficient as the basaltic host rock can be separated from the dyke material, resulting in a mass reduction of about 30% and a REE loss of less than 2%. Selective comminution experiments revealed similar results with the rejection of 27% of barren material and a slightly higher loss of REE (3.5%). Two step froth flotation of a model blend led to a concentrate with >40% TREO content.

Keywords: rare earth elements; Vietnam; processing

  • Lecture (Conference)
    GeoMin Köln 2022, 11.-15.09.2022, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35261
Publ.-Id: 35261


Modified HSE06 functional applied to anatase TiO2: influence of exchange fraction on the quasiparticle electronic structure and optical response

Lal Sb, S.; Devaraj, M.; Posselt, M.; Aravindh Sd, A.; Sharan, A.

The influence of non-interacting Kohn–Sham Hamiltonian on the non-self consistent GW(G0W0) quasiparticle gap and Bethe–Salpeter-equation (BSE) optical spectra of anatase TiO2 is systematically evaluated. G0W0 and BSE calculations are carried out starting with HSE06 (Heyd–Scuseria–Ernzerhof) type functionals containing 20%, 25% and 30% exact Hartree–Fock exchange. The results are also compared against G0W0 + BSE calculations starting from semi-local (PBE) functionals. Our results indicate that the G0W0 and BSE calculations of anatase TiO2 depend critically on the mean-field starting point, wherein its dependence is mainly introduced through the dielectric screening evaluated at the intermediate G0W0.We find that the band dispersion, density of states, and consequently the oscillator strengths of optical excitation and spatial localization of excitons are insensitive to the starting points while the quasiparticle gap, optical gap and exciton binding energies are strongly affected. G0W0 quasiparticle gap of anatase TiO2 computed over hybrid functional starting points is typically overestimated compared to measured values. However, by varying the amount of exact exchange, the dielectric screening can be tuned, and thus the quasiparticle gap. Exciton binding energy is shown to increase in proportion to the increase of the amount of exact exchange. A simple extrapolation of the calculated data leads to the exact match with the recently measured value with 13% of the exact exchange. Systematic analysis of G0W0 + BSE calculation starting from screened hybrid functionals provided in this study forms a reference for all such future calculations of pristine anatase TiO2 and its derivatives.

Keywords: HSE06 functional; anatase; exciton; optical properties; Bethe–Salpeter equation (BSE); G0W0; TiO2

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  • Secondary publication expected from 10.10.2023

Permalink: https://www.hzdr.de/publications/Publ-35260
Publ.-Id: 35260


Data and code for: Mitigating pseudoreplication and bias in resource selection functions with autocorrelation-informed weighting

Alston, J. M.; Fleming, C. H.; Kays, R.; Streicher, J. P.; Downs, C. T.; Ramesh, T.; Reineking, B.; Calabrese, J.

Data and code that can be used to reproduce the analyses underlying 'Mitigating pseudoreplication and bias in resource selection functions with autocorrelation-informed weighting' by Alston, Fleming, et al. (Preprint: https://doi.org/10.1101/2022.04.21.489059)

For more detailed information, please visit the README file.

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Permalink: https://www.hzdr.de/publications/Publ-35259
Publ.-Id: 35259


Density functionals with spin-density accuracy for open shells

Pearce, B.; Gidopoulos, N.; Callow, T. J.

Open-shell systems are normally described using spin density
functional theory (SDFT) rather than regular DFT, due to spinpolarised approximations appearing to yield superior results
for exchange-correlation (xc) energies. To address the seemingly poorer (xc) energies obtained via DFT approximations
(DFAs), we show that correcting for a qualitative error in the
DFT description for open-shell systems, one obtains results
with SDFT accuracy. Furthermore, in the absence of external magnetic fields, both DFT and SDFT should reduce to
the same limit. We provide the link between these two theories, demonstrating how the regular KS equations of SDFT
reduce to a new (generalised) set of KS equations for DFT in
this limit. We also extend these ideas to ensembles of varying
electron number, obtaining a finite derivative discontinuity for
commonly used (semi-)local DFAs.

  • Lecture (Conference)
    Psi-k conference 2022, 22.-25.08.2022, Lausanne, Swiss Confederation

Permalink: https://www.hzdr.de/publications/Publ-35258
Publ.-Id: 35258


The influence of sedimentary and diagenetic heterogeneity on the radionuclide diffusion in the sandy facies of the Opalinus Clay at the core scale

Yuan, T.; Fischer, C.

Molecular diffusion is an important transport mechanism for radionuclide migration in low-permeable argillaceous host rock such as Opalinus Clay (OPA). In this study, the influence of sedimentary and diagenetic heterogeneity on heterogeneous diffusion in sandy facies of OPA (SF-OPA) from lamina scale to drill core scale is investigated using an upscaling workflow to model diffusive transport from the pore scale to the core scale. Our numerical results based on the simplified structural model show fast diffusion fronts in clay laminae (7 mm displacement after 6 days of diffusion) and slow diffusion fronts in carbonate lenses and sand laminae (4 mm displacement after 6 days of diffusion), demonstrating the endmembers of heterogeneous diffusion patterns in SF-OPA. Moreover, our results show that the diffusion fronts begin to homogenize after 22 days of diffusion with the specific influence of carbonate lenses (here: length = 1 cm, thickness = 3 mm). This example illustrates how material heterogeneities affect heterogeneous diffusion on a small temporal and spatial scale. The sensitivity studies show that the diffusion length and homogenization time increase by up to 190% when the length and thickness of the carbonate lenses are doubled. Using four compositional endmembers, we show the generalized diffusion behavior to demonstrate the influence of thin laminae and thick layers as well as dispersed small and large diagenetic concretions on the homogeneity of diffusion. These results demonstrate that the geometry of sedimentary and diagenetic material and the subfacies composition are the controlling factors for quantifying diffusion length and homogenization time. This study provides quantitative constraints on the temporal and spatial evolution of heterogeneous diffusion at the core scale. This quantitatively improves the predictability of radionuclide migration in host rocks as a function of compositional and pore network-specific parameters.

Keywords: Contaminant migration; Heterogeneous diffusion; Sandy facies opalinus clay; Sedimentary and diagenetic heterogeneity; Nuclear waste disposal

Permalink: https://www.hzdr.de/publications/Publ-35257
Publ.-Id: 35257


Fast models for warm dense matter

Callow, T. J.; Kraisler, E.; Cangi, A.

The study of warm dense matter (WDM) is critical to our understanding of many interesting scientific and technological phenomena, in particular various astrophysical applications, and inertial confinement fusion. To develop accurate models for WDM, one has to account for the quantum behaviour of electrons (and sometimes nuclei too) across a wide range of temperatures and densities, which presents a challenge for established modelling techniques. In our poster, we introduce the concept of an average-atom model, which accounts (partially) for these quantum interactions in a computationally efficient way. We show some example applications of average-atom models, to demonstrate their usefulness in the WDM regime. We also present atoMEC: an average-atom code for matter under extreme conditions, which is open-source and written in Python.

  • Poster
    Big data analytical methods for complex systems, 06.-07.10.2022, Wrocław, Rzeczpospolita Polska

Permalink: https://www.hzdr.de/publications/Publ-35256
Publ.-Id: 35256


Benchmarking pressures and ionization states for an average-atom model under warm dense matter conditions

Callow, T. J.; Kraisler, E.; Cangi, A.

Average-atom models are an essential tool in modelling the warm dense matter regime, because they can be used to compute key quantities, such as equation-of-state data, for a fraction of the computational cost of higher-fidelity simulations such as DFT-MD. However, a variety of different models exist, and it is important to benchmark these models to understand their limitations and expected accuracy under various conditions. In this presentation, we focus on two key properties in WDM — the mean ionization state and pressure — for a range of materials, densities and temperatures. Through comparison with higher-fidelity simulations and experimental results, we probe the accuracy of an average-atom model, considering various choices of approximation within that model. We demonstrate a well-chosen average-atom model, under the right conditions, can yield close agreement with these benchmarks.

  • Lecture (Conference)
    Multiscale Modeling of Matter under Extreme Conditions, 11.-16.09.2022, Görlitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35255
Publ.-Id: 35255


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