Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Exotic band features, such as Dirac cones and flat bands, arise directly from the lattice symmetry of materials. The Lieb lattice is one of the most intriguing topologies, because it possesses both Dirac cones and flat bands which intersect at the Fermi level. However, the synthesis of Lieb lattice materials remains a challenging task. Here, we explore two-dimensional polymers (2DPs) derived from zinc-phthalocyanine (ZnPc) building blocks with a square lattice (sql) as potential electronic Lieb lattice materials. By systematically varying the linker length (ZnPc-xP), we found that some ZnPc-xP exhibit a characteristic Lieb lattice band structure. Interestingly though, fes bands are also observed in ZnPc-xP. The coexistence of fes and Lieb in sql 2DPs challenges the conventional perception of the structure–electronic structure relationship. In addition, we show that manipulation of the Fermi level, achieved by electron removal or atom substitution, effectively preserves the unique characteristics of Lieb bands. The Lieb Dirac bands of ZnPc-4P shows a non-zero Chern number. Our discoveries provide a fresh perspective on 2DPs and redefine the search for Lieb lattice materials into a well-defined chemical synthesis task.

In this study, the dissolution of a single oxygen bubble on a solid surface, here Titanium alloy Ti64, in ultrapure water with different oxygen undersaturation levels is investigated. For that purpose, a combination of shadowgraph technique and planar laser-induced fluorescence is used to measure simultaneously the changes in bubble geometry and in the dissolved oxygen concentration around the bubble. Two different wettabilities of the Ti64 surface are adjusted by using plasma-enhanced chemical vapor deposition. The dissolution process on the solid surface involves two distinct phases, namely bouncing of the oxygen bubble at the Ti64 surface and the subsequent dissolution of the bubble, primarily by diffusion. By investigating the features of oxygen bubbles bouncing, it was found that the boundary layer of dissolved oxygen surrounding the bubble surface is redistributed by the vortices emerging during bouncing. This establishes the initial conditions for the subsequent second dissolution phase of the oxygen bubbles on the Ti64 surfaces. In this phase, the mass transfer of O2 proceeds non-homogeneously across the bubble surface, leading to an oxygen accumulation close to the Ti64 surface. We further show that the main factor influencing the differences in the dynamics of O2 bubble dissolution is the variation in the surface area of the bubbles available for mass transfer, which is determined by the substrate wettability. As a result, dissolution proceeds faster at the hydrophilic Ti64 surface due to the smaller contact angle, which provokes a larger surface area.

At the electron accelerator for beams with high brilliance and low emittance (ELBE), the second version of a superconducting radio-frequency (SRF) photoinjector was brought into operation in 2014. After a period of commissioning, a gradual transfer to routine operation took place in 2017, so that now more than 1800h of user beam are generated every year. In addition to this routine operation with a few tens of microamperes, another important goal, the generation of an average current of 1 mA, which is high for electron linear accelerators, could now be demonstrated with our SRF gun. At the same time, this beam was already accelerated to almost 30 MeV by the ELBE LINAC and irradiated in one of the IR-FELs. This is particularly important with regard to the successor of the ELBE accelerator called DALI, which will be also fed by an SRF gun with a high average current. The contribution presents the most important steps for achieving the full beam current and summarizes related measurement results and findings. No fundamental difficulties were identified.

As the physicochemical properties of ultrafine bubble systems are governed by their size, it is crucial to determine the size and distribution of such bubble systems. At present, the size or size distribution of nanometer-sized bubbles in suspension is often measured by either dynamic light scattering or the nanoparticle tracking analysis. Both techniques determine the bubble size via the Einstein–Stokes equation based on the theory of the Brownian motion. However, it is not yet clear to which extent the Einstein–Stokes equation is applicable for such ultrafine bubbles. In this work, using atomic molecular dynamics simulation, we evaluate the applicability of the Einstein–Stokes equation for gas nanobubbles with a diameter less than 10 nm, and for a comparative analysis, both vacuum nanobubbles and copper nanoparticles are also considered. The simulation results demonstrate that the diffusion coefficient for rigid nanoparticles in water is found to be highly consistent with the Einstein–Stokes equation, with slight deviation only found for nanoparticle with a radius less than 1 nm. For nanobubbles, including both methane and vacuum nanobubbles, however, large deviation from the Einstein–Stokes equation is found for the bubble radius larger than 3 nm. The deviation is attributed to the deformability of large nanobubbles that leads to a cushioning effect for collision-induced bubble diffusion.

We provide an extended lattice study of the SU(2) gauge theory coupled to one Dirac fermion flavour (Nf=1Nf​=1) transforming in the adjoint representation as the continuum limit is approached. This investigation is supplemented by numerical results obtained for the SU(2) gauge theory with two Dirac fermion flavours (Nf=2Nf​=2) transforming in the adjoint representation, for which we perform numerical investigations at a single lattice spacing value, which is analysed together with earlier calculations. The purpose of our study is to advance the characterisation of the infrared properties of both theories, which previous investigations have concluded to be in the conformal window. For both, we determine the mass spectrum and the anomalous dimension of the fermion condensate using finite-size hyperscaling of the spectrum, mode number analysis of the Dirac operator (for which we improve on our previous proposal) and the ratio of masses of the lightest spin-2 particle over the lightest scalar. All methods provide a consistent picture, with the anomalous dimension of the condensate γ∗γ∗​ decreasing significantly as one approaches the continuum limit for the Nf=1Nf​=1 theory towards a value consistent with γ∗=0.174(6)γ∗​=0.174(6), while for Nf=2Nf​=2 the anomalous dimension decreases more slowly with ββ. A chiral perturbation theory analysis show that the infrared behaviour of both theories is incompatible with the breaking of chiral symmetry.

The Dresden laser acceleration source (DRACO) is a state-of-the-art high-power ultra-short pulse laser system[1,2],
that uses an Amplitude Technologies Pulsar architecture to form main and diagnostics beams at different focal lengths and target density conditions.
The setup can deliver from 6J to 45J of pulse energy at a typical pulse duration of 30fs and a typical frequency of 1Hz.
During the diagnostic phase, the beam characteristics are recorded in the form of images and several instrument parameters,
that shape the beam to desired characteristics.

In this talk, we present our approach of implementing FAIR principles to DRACO
operations and monitoring using our in-house guidance system HELIPORT[3],
with the goal of making them reusable irrespective of the downstream experiment.
We employ FAIR workflows[4] to post-process data collected by DRACO's built-in data
acquisition system and enrich it with metadata for subsequent utilization in
machine-learning and optimization algorithms for accurate control of the beam characteristics.
The intergration of DRACO and HELIPORT demonstrates the first step towards establishing
a digital twin for the laser source facility at HZDR.

[1] First results with the novel Petawatt laser acceleration facility in Dresden, U. Schramm et al, J. Phys. Conf. Ser. 874 012028 (2017)
[2] High dynamic, high resolution and wide range single shot temporal pulse contrast measurement, T. Oksenhendler et. al., Opt. Express 25, 12588-12600 (2017)
[3] HELIPORT: A Portable Platform for FAIR {Workflow | Metadata | Scientific Project Lifecycle} Management and Everything, O. Knodel et. al., P-RECS (2021)
[4] FAIR Computational workflows, C. Goble et. al., Data Intelligence (2020) 2, 108 (2020)

The very limited number of structurally known thionitrosyl complexes of technetium was increased by the synthesis of [Tcᴵᴵ(NS)Cl₃(PPh₃)₂] (3) and [Tcᴵᴵ(NS)Cl₃(PPh₃)(OPPh₃)] (4) and their reaction products with hydrotris(pyrazolyl)borates, {HB(pzᴿ)₃}⁻. Similar reactions were conducted with [Tcᴵ(NO)Cl₂(PPh₃)₂(CH₃CN)] and related rhenium thionitrosyls. Remarkably, most such reactions result in a rapid cleavage of the boron–nitrogen bonds of the ligands and the formation of pyrazole complexes of the two group 7 metals. Only one compound with an intact {HB(pzᴿ)₃}⁻ ligand could be isolated: the technetium(I) complex [Tcᴵ(NO)Cl(PPh₃){HB(pz)₃}] (2). Other products show the coordination of one or four neutral pyrazole ligand(s) in the coordination spheres of technetium generated by thermal decomposition of the pyrazolylborates [Tcᴵ(NO)Cl₂(PPh₃)₂(pzᴴ)] (1) and [Tcᴵ(NS)Cl(pzᴴᴹᵉ²)₄]⁺ (5). Reactions with the corresponding thionitrosylrhenium complex [Reᴵᴵ(NS)Cl₃(PPh₃)₂] require higher temperatures and only compounds with one pyrazole ligand, [Reᴵ(NS)Cl₂(PPh₃)(pzᴴᴿ)] (6a–6c), were isolated. The products were studied spectroscopically and by X-ray diffraction.

Amonton's law of friction states that the friction force is proportional to the normal force in magnitude, and the slope gives a constant friction coefficient. In this work, with molecular dynamics simulation, we study how the kinetic friction at the nanoscale deviates qualitatively from the relation. Our simulation demonstrates that the friction behavior between a nanoscale AFM tip and an elastic graphene surface is regulated by the coupling of the applied normal force and the substrate deformability. First, it is found that the normal load-induced substrate deformation could lower friction at low load while increasing it at high load. In addition, when the applied force exceeds a certain threshold another abrupt change in friction behavior is observed, i.e., the stick–slip friction changes to the paired stick–slip friction. The unexpected change in friction behavior is then ascribed to the change of the microscopic contact states between the two surfaces: the increase in normal force and the substrate deformability together lead to a change in the energy landscape experienced by the tip. Finally, the Prandtl–Tomlinson model also validates that the change in friction behavior can be interpreted in terms of the energy landscape.

The structural and magnetic properties of sputter-deposited Fe_100−xRu_x films were studied for x < 50. The crystal structure of Fe_100−xRu_x is shown to be predominantly body-centered cubic for x < 13 and to undergo a gradual transition to hexagonal close-packed in the Ru concentration range 13 < x < 20. Magnetic measurements indicate that the addition of Ru to Fe gives rise to a noncollinear magnetic alignment between Fe atoms in the body-centered cubic FeRu alloys, while the hexagonal close-packed FeRu alloys exhibit paramagnetic behavior. A simple atomistic model was used to show that the competition between ferromagnetic coupling of neighboring Fe atoms and antiferromagnetic coupling of Fe atoms across Ru atoms in cubic FeRu structures can induce noncollinear magnetic order. Magnetic multilayer structures used in thin-film magnetic devices make extensive use of both Fe and Ru layers. Our results reveal that the presence of even a small amount of Ru in Fe influences the magnetic order of Fe, which could impact the performance of these devices.

Highly simplified electrolyzer designs in the form of a membraneless alkaline electrolyzer (MAEL) allow higher current densities compared to conventional designs and result as well in lower capital expenditures. In addition, MAELs provide very good access to the electrodes, making them ideal for research to better understand bubble formation and detachment. Since there is no membrane or diaphragm to separate the products, H2 and O2, the cell design to direct the electrolyte flow is critical.

Using CFD and current simulations, an optimized cell geometry was developed to ensure constant conditions for the water splitting reaction over the entire electrode. Particle Image Velocimetry and Shadowgraphy were used to systematically study the influence of the electrolyte flow as driving force for an effective H2 and O2 separation. It is shown that below a critical Recrit the evolving bubbles are stuck on the porous electrodes and lead to a blockage of electrochemical active sites as well as to an increase of the cell potential. On the other hand, high gas purity and overall efficiency were observed at the optimal flow rate to current density ratio. Thus, the present study proves the concept of the newly developed membraneless electrolyzer.

Historically, cerium has been attractive for pharmaceutical and
industrial applications. The cerium atom has the unique ability
to cycle between two chemical states (Ce(III) and Ce(IV)) and
drastically adjust its electronic configuration: [Xe] 4f15d16s2 in
response to a chemical reaction. Understanding how electrons
drive chemical reactions is an important topic. The most direct
way of probing the chemical and electronic structure of
materials is by X-ray absorption spectroscopy (XAS) or X-ray
absorption near-edge structure (XANES) in high energy reso-
lution fluorescence detection (HERFD) mode. Such measure-
ments at the Ce L3 edge have the advantage of a high
penetration depth, enabling in-situ reaction studies in a time-
resolved manner and investigation of material production or
material performance under specific conditions. But how much
do we understand Ce L3 XANES? This article provides an
overview of the information that can be extracted from
experimental Ce L3 XAS/XANES/HERFD data. A collection of
XANES data recorded on various cerium systems in HERFD
mode is presented here together with detailed discussions on
data analysis and the current status of spectral interpretation,
including electronic structure calculations.

he preparation of synthetic (Zr,U)SiO4 solid solution is challenging, as the conventional high-temperature
solid-state method limits the solubility of uranium (4 ± 1 mol%) in the orthosilicate phase due to its
thermodynamic instability. However, these compounds are of great interest as a result of (Zr,U)SiO4 solid
solutions, with uranium contents exceeding this concentration, being observed as corium phases formed
during nuclear accidents. It has been identified that hydrothermal synthesis pathways can be used for the
formation of the metastable phase, such as USiO4 . The investigation carried out in this study has indeed
led to the confirmation of metastable (Zr,U)SiO4 compounds with high uranium contents being formed. It
was found that (Zr,U)SiO4 forms a close-to-ideal solid solution with uranium loading of up to 60 mol% by
means of hydrothermal treatment for 7 days at 250 °C, at pH = 3 and starting from an equimolar reactant
concentration equal to 0.2 mol L−1 . A purification procedure was developed to obtain pure silicate com-
pounds. After purification, these compounds were found to be stable up to 1000 °C under an inert atmo-
sphere (argon). The characterisation methods used to explore the synthesis and thermal stability included
powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) and Raman spectroscopies, scanning
electron microscopy (SEM) and thermogravimetric analysis (TGA).

Understanding the electrical conductivity of warm dense hydrogen is critical for both fundamental physics and applications in planetary science and inertial confinement fusion. We demonstrate how to calculate the electrical conductivity using the continuum form of Ohm's law, with the current density obtained from real-time time-dependent density functional theory. This approach simulates the dynamic response of hydrogen under warm dense matter conditions, with temperatures around 30,000 K and mass densities ranging from 0.02 to 0.98 g/cc. We systematically address finite-size errors in real-time time-dependent density functional theory, demonstrating that our calculations are both numerically feasible and reliable. Our results show good agreement with other approaches, highlighting the effectiveness of this method for modeling electronic transport properties from ambient to extreme conditions.

Profile analysis tensiometry (PAT) with drops and bubbles is a successful methodology to characterize liquid–fluid interfaces. Questions about the most suitable size of drops and bubbles have been solved now on the basis of dimensionless numbers. The consideration of the standard deviation between measured and calculated liquid profiles as a sensitive measure for the applicability of PAT provides a tool for its correct use. For solutions of highly surface-active compounds, bulk depletion effects can cause systematic errors in the analysis of adsorption kinetics, equations of state, and the visco-elastic interfacial behavior of liquid adsorption layers. Great progress has been made in measurements of interfacial dilational rheology with large amplitude perturbations providing additional information about structure and dynamics of complex adsorption layers. Also, first attempts are successfully made to use artificial intelligence (AI) to enhance the efficiency of PAT applications. Thus, PAT has established a solid position in surface science.

The establishment of inhaled aerosols plays a significant role in risk assessment regarding air pollution and spreading of diseases. It is also of importance for evaluating lung deposition of particles and hence, the effectiveness of inhaled drug delivery systems. When it comes to air pollution or airborne diseases, there is a broad discussion whether ventilation by frequent window opening is sufficient for providing a sufficient amount of fresh air or if technical air purification devices based on e.g. HEPA filters are page better solutions for public spaces. Furthermore, there is another discussion ongoing, whether a well-guided laminar flow or a high degree of mixing within a room is more beneficial. The latter, on the one hand distributes the potentially virus-laden aerosols in the whole room, but on the other hand reduces the peak concentrations of these aerosols clouds by magnitudes.

The objective of this study is to answer to these queries by performing aerosol propagation experiments in order to estimate the potential aerosol inhalation of people in dynamic situations. To achieve this, an aerosol generator is used for aerosolizing a solution of water/MgCl2, which is collected in removible filters located in breathing masks used by the people during the experiment. The quantification of the inhaled aerosol is carried out by extracting the Mg from the mask and measuring it using inductively coupled plasma mass spectromestry technique (ICP-MS). Experiments will be performed in a demonstrator room under different flow conditions. The data from different scenarios will be processed in order to obtain a transference function that can relate the aerosol source with the aerosol receivers.

Background: Hypoxia remains a challenge for the therapeutic management of head and neck squamous cell carcinoma (HNSCC). The combination of radiotherapy with nimorazole has shown treatment benefit in HNSCC, but the precise underlying molecular mechanisms remain unclear. Purpose: To assess and to characterize the transcriptomic/epigenetic landscape of HNSCC tumor models showing differential therapeutic response to fractionated radiochemotherapy (RCTx) combined with nimorazole. Materials/methods: Bulk RNA-sequencing and DNA methylation experiments were conducted using untreated and treated HNSCC xenografts after 10 fractions of RCTx with and without nimorazole. These tumor models (FaDu, SAS, Cal33, SAT and UT-SCC-45) previously showed a heterogeneous response to RCTx with nimorazole. The prognostic impact of candidate genes was assessed using clinical and gene expression data from HNSCC patients treated with primary RCTx within the DKTK-ROG. Results: Nimorazole responder and non-responder tumor models showed no differences in hypoxia gene signatures However, non-responder models showed upregulation of metabolic pathways. From that, a subset of 15 differentially expressed genes stratified HNSCC patients into low and high-risk groups with distinct outcome. Conclusion: In the present study, we found that nimorazole non-responder models were characterized by upregulation of genes involved in Retinol metabolism and xenobiotic metabolic process pathways, which might contribute to identify mechanisms of resistance to nitroimidazole compounds and potentially expand the repertoire of therapeutic options to treat HNSCC.

I present an overview of current ab initio path integral Monte Carlo (PIMC) capabilities to simulate warm dense matter and related extreme states. In the first part, I introduce the PIMC method and summarize recent developments for the uniform electron gas. In the second part, I show how emerging PIMC simulations of real systems such as warm dense hydrogen and beryllium allow for novel ways to interpret x-ray Thomson scattering (XRTS) measurements. This is demonstrated for an experimental dataset for strongly compressed beryllium measured at the National Ignition Facility (NIF).

Deuterium insertion was used to tune the magnetic properties of Y_0.9Tb_0.1Fe₂ Laves phase towards an itinerant electron metamagnetic (IEM) behavior. The latter is highly sensitive to chemical changes and external parameters. The structural and magnetic properties of Y_0.9Tb_0.1Fe₂D_4.3 were investigated using various neutron powder diffraction experiments in addition to magnetic measurements under steady and pulsed high magnetic fields up to 60 T. The deuteride crystallizes in a monoclinic structure (P_c space group) with 4.3 D atoms located in 18 tetrahedral interstitial sites. At zero field, it undergoes a ferrimagnetic-antiferromagnetic (FiM-AFM) transition at T_M0 = 90 K, accompanied by an anisotropic magnetostriction and a negative cell volume expansion of 0.6 %. A second AFM-PM transition is observed at 146 K. Under pulsed magnetic field at 4.2 K, the deuteride displays a multistep magnetic behavior from ferrimagnetic to a ferromagnetic state, which can be attributed to a stepwise rotation of the Tb moments. The ZFC-FC magnetization curves at low fields exhibit an irreversibility below 90 K, followed by a sharp decrease in magnetization at the FM-AFM transition. Between 90 K and 130 K, the magnetization curves display an IEM behavior, with the transition field increasing linearly with temperature.

In spatially inverted systems, the complex entanglement of Dzyaloshinskii-Moriya interaction (DMI) and other magnetic anisotropies, mediated by spin-orbit coupling (SOC), influences the emergence and dynamics of the chiral spin textures such as skyrmion. The competing and unified effect of these anisotropies - which is expected to amplify the skyrmionics response in the quantum transport phenomena - is not yet known. Here, we investigate this template and engineer the topological Hall effect (THE) arising from chiral spin texture in a range of La_0.7Sr_0.3MnO₃/CaIrO₃ superlattices. The strength of SOC and interfacial DMI are controlled via the architectural design and charge transfer across the interface. All the superlattices display anomalous Hall effect, accompanied by the hump like feature. In (L₃I_y)₄ (y = 4, 6, and 8) superlattices, the humplike feature that is deemed as the THE is intrinsic in nature and stems from the chiral spin texture. For the intermediate strength of SOC, unique eightfold anisotropic magnetoresistance oscillations manifest owing to the modulation of the magnetic easy axis in the presence of competing anisotropies. For this superlattice, THE shows remarkable enhancement of the order such that it takes complete precedence over anomalous contribution. The thicker superlattice with higher fraction of charge transfer augments ferromagnetic interactions, and the artificial THE appears as a consequence of a dual-channel anomalous Hall effect. This manipulation of the THE is intricately connected to the concurrent presence of magnetic anisotropies, altering the dynamics of chiral spin texture. These findings expand the understanding of the corroborative contributions of competing anisotropies and yield a comprehensive control of chiral properties - a dimension for the utility in next-generation spintronics technologies.

The Remote Sensing (RS) field continuously grapples with the challenge of transforming satellite data into actionable information. This ongoing issue results in an ever-growing accumulation of unlabeled data, complicating interpretation efforts. The situation becomes even more challenging when satellite data must be used immediately to identify the effects of a natural hazard. Self-supervised learning (SSL) offers a promising approach for learning image representations without labeled data. Once trained, an SSL model can address various tasks with significantly reduced requirements for labeled data. Despite advancements in SSL models, particularly those using contrastive learning methods like MoCo, SimCLR, and SwAV, their potential remains largely unexplored in the context of instance segmentation and semantic segmentation of satellite imagery. This study integrates SwAV within an auto-encoder framework to detect landslides using deca-metric resolution multi-spectral images from the globally-distributed large-scale landslide4sense (L4S) 2022 benchmark dataset, employing only 1% and 10% of the labeled data. Our proposed SSL auto-encoder model features two modules: SwAV, which assigns features to prototype vectors to generate encoder codes, and ResNets, serving as the decoder for the downstream task. With just 1% of labeled data, our SSL model performs comparably to ten state-of-the-art deep learning segmentation models that utilize 100% of the labeled data in a fully supervised manner. With 10% of labeled data, our SSL model outperforms all ten fully supervised counterparts trained with 100% of the labeled data.

Research software is a central pillar in the scientific work in general, in the Helmholtz Association and in particular at the Helmholtz-Zentrum Dresden - Rossendorf e.V. (HZDR). The software policy at the HZDR supports researchers in their independence and ability to act and is a framework that provides orientation. It gives advice and makes recommendations for the whole software lifecycle from development and documentation to publication and distribution as well as maintenance of the research software.

The HZDR software policy is derived from a model policy provided by the Task Group Research Software of the Helmholtz Open Science Office. Adaptations were made, for example, regarding the recommended software quality ensurance measures based on the software application classes suggested by the German Aerospace Center (DLR) as well as the choice of Open-Source Software (OSS) licenses. A selection process and decision tree were defined to recommend the preferred use a specific set of OSS licenses at the HZDR.

The introduction of a policy at HZDR and for each of the research centres in the Helmholtz Association involves not only behavioural but also cultural change in the whole research association and all related research groups. The overall objectives are to achieve better sustainability and higher quality in research software engineering leading to better verifiability, traceability and reproducibility of scientific results.

The electron-phonon interaction is in many ways a solid state equivalent of quantum electrodynamics. Being always present, the e-p coupling is responsible for the intrinsic resistance of metals at finite temperatures, making it one of the most fundamental interactions present in solids. In typical metals, different regimes of e-p scattering are separated by a characteristic phonon energy scale—the Debye temperature. However, in metals harboring very small Fermi surfaces a new scale emerges—the Bloch-Grüneisen temperature. This is a temperature at which the average phonon momentum becomes comparable to the Fermi momentum of the electrons. Here we report sub-Kelvin transport and sound propagation experiments on the Dirac semimetal ZrTe₅. The combination of the simple band structure with only a single small Fermi surface sheet allowed us to directly observe the Bloch-Grüneisen temperature and its consequences on electronic transport of a 3D metal in the limit where the small size of the Fermi surface leads to effective restoration of translational invariance of free space. Our results indicate that on entering this hydrodynamic transport regime, the viscosity of the Dirac electronic liquid undergoes an anomalous increase beyond the theoretically predicted T⁵ temperature dependence. Extension of our measurements to strong magnetic fields reveal that, despite the dimensional reduction of the electronic band structure, the electronic liquid retains characteristics of the zero-field hydrodynamic regime up to the quantum limit. This is vividly reflected by an anomalous suppression of the amplitude of quantum oscillations seen in the Shubnikov-de Haas effect.

We investigated the magnetic and magnetoelastic properties of MnSc₂Se₄ single crystals at low temperature under a magnetic field directed along the crystallographic [111] axis. The magnetization data at low temperature show a linear increase with magnetic field, until saturation is reached above 15 T. In ultrasound, a longitudinal acoustic mode shows a softening in field, which is absent for a transverse acoustic mode.We discuss these results using a microscopic model based on the framework of linear spin-wave theory. The magnetic and magnetoelastic data are qualitatively reproduced by considering magnon-phonon interactions arising from exchange-striction coupling between the crystal lattice and spin-wave fluctuations in the zero-temperature limit.

Spinon-magnon mixing was recently reported in botallackite Cu₂(OH)₃Br with a uniaxially compressed triangular lattice of Cu²⁺ quantum spins [H. Zhang et al., Phys. Rev. Lett. 125, 037204 (2020)]. Its nitrate counterpart rouaite, Cu₂(OH)₃NO₃, has a highly analogous structure and might be expected to exhibit similar physics. To lay a foundation for research on this material, we clarify rouaite’s magnetic phase diagram and identify both low-field phases. The low-temperature magnetic state consists of alternating ferromagnetic and antiferromagnetic chains, as in botallackite, but with additional canting, leading to net moments on all chains which rotate from one chain to another to form a 90° cycloidal pattern. The higher-temperature phase is a helical modulation of this order, wherein the spins rotate from one Cu plane to the next. This extends to zero temperature for fields perpendicular to the chains, leading to a set of low-temperature field-induced phase transitions. Rouaite may offer another platform for spinon-magnon mixing, while our results suggest a delicate balance of interactions and high tunability of the magnetism.

We present a thorough experimental investigation on single crystals of the rare-earth based frustrated quantum antiferromagnet Pr₃BWO₉, a purported spin-liquid candidate on the breathing kagome lattice. This material possesses a disordered ground state with an unusual excitation spectrum involving a coexistence of sharp spin waves and broad continuum excitations. Nevertheless, we show through a combination of thermodynamic, magnetometric, and spectroscopic probes with detailed theoretical modeling that it should be understood in a completely different framework. The crystal field splits the lowest quasidoublet states into two singlets moderately coupled through frustrated superexchange, resulting in a simple effective Hamiltonian of an Ising model in a transverse magnetic field. While our neutron spectroscopy data do point to significant correlations within the kagome planes, the dominant interactions are out-of-plane, forming frustrated triangular spin-tubes through two competing ferro-antiferromagnetic bonds. The resulting ground state is a simple quantum paramagnet, where the presence of strongly hyperfine-coupled nuclear moments and weak structural disorder causes significant modifications to both thermodynamic and dynamic properties.

Recent promising results from inertial fusion energy (IFE) facilities, such as the National Ignition Facility in the USA, have sparked a strong interest in IFE technologies. Because it is a multiscaled problem from a simulation standpoint, significant effort is required to accurately model the dense plasmas on various length and time scales, which is crucial for developing IFE technology. One of the main challenges in modeling is creating reliable simulation tools to study the dynamic dielectric and transport properties of dense plasmas across different temperature and density ranges. Quantum many-body theory is crucial in developing a dependable method for computing these properties, provided the density response function of plasmas is known. This presentation discusses the advanced simulation methods being used and developed at the Center of Advanced Systems Understanding [1-4] for this property and the associated computational and work expenses.

[1] Tobias Dornheim, Zhandos A. Moldabekov, Kushal Ramakrishna, Panagiotis Tolias, Andrew D. Baczewski, Dominik Kraus, Thomas R. Preston, David A. Chapman, Maximilian P. Böhme, Tilo Döppner, Frank Graziani, Michael Bonitz, Attila Cangi, Jan Vorberger, Electronic density response of warm dense matter, Phys. Plasmas 30, 032705 (2023).
[2] Zhandos Moldabekov, Jan Vorberger, Tobias Dornheim, Density Functional Theory Perspective on the Nonlinear Response of Correlated Electrons across Temperature Regimes, J. Chem. Theory Comput. 2022, 18, 5, 2900–2912
[3] Zhandos A. Moldabekov, Michele Pavanello, Maximilian P. Böhme, Jan Vorberger, and Tobias Dornheim, Linear-response time-dependent density functional theory approach to warm dense matter with adiabatic exchange-correlation kernels, Phys. Rev. Research 5, 023089 (2023)
[4] Maximilian Böhme, Zhandos A. Moldabekov, Jan Vorberger, and Tobias Dornheim, Static Electronic Density Response of Warm Dense Hydrogen: Ab Initio Path Integral Monte Carlo Simulations, Phys. Rev. Lett. 129, 066402 (2022)

In this experimental study, we explore the dynamics of the thermal boundary layer in liquid metal Rayleigh–Bénard convection, covering the parameter ranges of 0.026 ≤ Prandtl numbers (Pr) ≤0.033 and Rayleigh numbers (Ra) up to 2.9×10^9. Our research focuses on characterising the thermal boundary layer near the top plate of a cylindrical convection cell with an aspect ratio of 0.5, distinguishing between two distinct regions: the shear-dominated region around the centre of the top plate and a location near the side wall where the boundary layer is expected to be affected by the impact or ejection of thermal plumes. The dependencies of the boundary layer thickness on Ra at these positions reveal deviating scaling exponents with the difference diminishing as Ra increases. We find stronger fluctuations in the boundary layer and increasing deviation from the Prandtl–Blasius–Pohlhausen profile with increasing Ra, as well as in the measurements outside the centre region. Our data illustrate the complex interplay between flow dynamics and thermal transport in low-Pr convection.

Magnetic refrigeration based on the principle of the magnetocaloric effect (MCE) in magnetic solids has been considered as a prospective cooling technology. Exploring suitable magnetocaloric materials (MCMs) is a vital prerequisite for practical applications. Herein, an excellent cryogenic MCM—the B-site-ordered Gd₂CuTiO₆ double perovskite (DP) oxide—which exhibits the largest MCE among known Gd-based DP oxides, is identified. Such enhanced cryogenic MCE in the Gd₂CuTiO₆ DP oxide likely stems from the exchange interaction effect between Gd-4f and Cu-3d magnetic sublattices. Under a magnetic field change of 0–7 T, the maximum magnetic entropy change (−ΔS_T ^max) of the Gd₂CuTiO₆ DP oxide reaches 51.4 J kg⁻¹ K⁻¹ (378.2 mJ cm⁻³ K⁻¹), which is much larger than that of the commercialized magnetic refrigerant Gd₃Ga₅O₁₂, which is 38.3 J kg⁻¹ K⁻¹ (271.2 mJ cm⁻³ K⁻¹), and it is also superior to most of the recently reported benchmarked cryogenic MCMs, indicating the possibility for practical applications. This work also provides a productive route for future cryogenic MCM design by harnessing 4f–3d exchange interactions.

In case it is desirable to dispose of inventories of separated civil PuO2 that have no further use, a
suitable immobilisation matrix is required, prior to disposition in a geological disposal facility. Conversion
of Pu into a mixed oxide (MOX)-type material with characteristics suitable for disposal has previously
been suggested, but not yet demonstrated at laboratory or industrial scale. We here demonstrate the
feasibility of different synthesis routes for simulant ‘‘disposal-MOX’’, using Th 4+ as a Pu4+ surrogate and
containing Gd3+ in a suitable quantity to ensure criticality control. Compositions of (U(1(x+y))ThxGdy)O2d,
where x = 0.1, 0.2 and x : y = 10 : 1 or 100 : 1, were synthesised by a solid state route mimicking the industrial
MIMAS MOX fuel fabrication process, or through an oxalic wet co-precipitation
method. Both synthesis routes gave a single phase fluorite structure upon heat-treatment at 1700 1C, with a
grain size similar to (Pu,U)O2 MOX fuel. The relative density of the sintered pellets was 490% but was
highest in co-precipitated materials, with Th4+ and Gd3+ additions more homogenously distributed. Though
no unincorporated ThO2 or Gd2O3 was observed in any sample, Th and Gd-rich regions were more
prevalent in materials produced through solid state synthesis, in accordance with MIMAS MOX fuel
microstructures. The incorporation of Gd3+ within the fluorite lattice, which is favourable from a criticality
control perspective in a Pu wasteform, was found to be charge balanced via the generation of oxygen
vacancy defects, but not U5+. These results demonstrate feasible synthesis routes for a disposal-MOX
wasteform product via both solid state and wet co-precipitation fabrication routes.

Positron annihilation spectroscopy (PAS) is a precise probe of point defects in bulk and nanomaterials, such as semiconductors. Positrons localize in the neutral and negatively charged open volume defects, i.e. vacancies and their agglomerations, extended defects or pores. The time to the inevitable annihilation of the positron with the electron depends on the local electron density and scales with the open volume size. Positrons pre-accelerated to a given kinetic energy are implanted into solids, allowing depth profiling. In a defect, their lifetime increases and the energetics of the annihilation photons changes. These characteristics are measured using two main measurement techniques, namely positron annihilation lifetime spectroscopy (PALS) and coincidence Doppler broadening spectroscopy (cDBS or cDB-PAS), respectively. Both techniques are available at the large-scale user facility ELBE at HZDR, Germany. PALS allows the evaluation of defect size and concentration, while cDBS provides sensitivity to positron annihilation with valence and core electrons, the latter a fingerprint of the nearest neighbor atoms.
This contribution discusses the role of open volume defects and defect chemistry in the context of heavily doped semiconductors, such as sulfur- and telluride-doped GaAs [1] and Si [2], Al doped ZnO (AZO) [3], or pulsed laser and flash lamp annealed GeSn [4]. We will show that incomplete recrystallization processes resulting from intense pulsed laser melting (PLM) and flash lamp annealing (FLA) are related to defect distribution and electrical activation efficiency in chalcogenide-implanted GaAs. Similarly, in thermally treated chalcogenide-implanted Si, vacancy accumulation processes correlate with variations in carrier concentration and electron mobility. A combination of PAS measurements and DFT calculations allows to translate the experimental results into defect types/sizes and highlights the role of vacancy-dopant complexes for electrical deactivation. On the other hand, the relationship between the crystal quality of AZO films, i.e. single, polycrystalline or amorphous structures, and deposition parameters, such as growth pressure and thickness, can be related to the concomitant increase in vacancy agglomeration size and density. We will discuss the role of dislocations and Sn-decorated germanium vacancies, resulting from Sn diffusion and clustering due to PLM, on the electrical properties of GeSn. The change in defect microstructure depending on the Sn content will be highlighted, too. Finally, a new perspective for PAS is given, where the simultaneous light illumination together with positron measurements will allow new insights into sub-bandgap defect levels in semiconductors, e.g. in GaN.
[1] J. Duan et al., J. Appl. Phys., 134 (2023) 95102
[2] M.S. Shaikh et al., Appl. Surf. Sci., 567 (2021) 150755
[3] R.M. Maffei et al., Appl. Surf. Sci., 665 (2024) 160240
[4] O. Steuer et al., J. Phys. Condens. Matter, 36 (2024) 085701

In contrast to corresponding nitrosyl compounds, thionitrosyl complexes of rhenium and technetium are rare. Synthetic access to the thionitrosyl core is possible by two main approaches: (i) the treatment of corresponding nitrido complexes with S₂C₂ and (ii) by reaction of halide complexes with trithiazyl chloride. The first synthetic route was applied for the synthesis of novel rhenium and technetium thionitrosyls with the metals in their oxidation states “+1” and “+2”. [MᵛNCl₂(PPh₃)₂], [MᵛNCl(PPh₃)(LOMe)] and [MᵛᶦNCl₂(LOMe)] (M = Re, Tc; {LOMe}⁻ = (η⁵-cyclopentadienyl)tris(dimethyl phosphito-P)cobaltate(III)) complexes have been used as starting materials for the synthesis of [Reᴵᴵ(NS)Cl₃(PPh₃)₂] (1), [Reᴵᴵ(NS)Cl₃(PPh₃)(OPPh₃)] (2), [Reᴵᴵ(NS)Cl(PPh₃)(LOMe)]⁺ (4a), [Reᴵᴵ(NS)Cl₂(LOMe)] (5a), [Tcᴵᴵ(NS)Cl(PPh₃)(LOMe)]⁺ (4b) and [Tcᴵᴵ(NS)Cl₂(LOMe)] (5b). The triphenylphosphine complex 1 is partially suitable as a precursor for ongoing ligand exchange reactions and has been used for the synthesis of [Reᴵ(NS)(PPh₃)(Et₂btu)₂] (3a) (HEt₂btu = N,N-diethyl-N′-benzoyl thiourea) containing two chelating benzoyl thioureato ligands. The novel compounds have been isolated in crystalline form and studied by X-ray diffraction and spectroscopic methods including IR, NMR and EPR spectroscopy and (where possible) mass spectrometry. A comparison of structurally related rhenium and technetium complexes allows for conclusions about similarities and differences in stability, reaction kinetics and redox behavior between these 4d and 5d transition metals.

Die Protonentherapie zeichnet sich durch steile Dosisgradienten und damit einen gut lokalisierbaren Energieübertrag aus. Um dieses Potential voll ausschöpfen zu können, werden weltweit Möglichkeiten erforscht, die Dosisdeposition und insbesondere die Reichweite der Protonen im Patienten zu verifizieren. Eine vielversprechende, erst im letzten Jahrzehnt entdeckte Methode ist das Prompt Gamma-Ray Timing (PGT), das auf der Abhängigkeit der detektierten Flugzeitverteilung prompter Gammastrahlung von der Transitzeit der Protonen im Patienten beruht. In dieser Arbeit wird eine Geant4-Simulation zur Vorhersage der PGT-Spektren bei Bestrahlung eines PMMA-Phantoms entwickelt und durch den Vergleich mit experimentellen Daten validiert. Sowohl die Emissionsausbeute prompter Gammastrahlung im Phantom als auch die Detektionsrate werden abhängig von der Protonenenergie analysiert. Zur Vergleichbarkeit mit den gemessenen Spektren wird eine mehrschrittige Prozessierung der Simulationsergebnisse vorgestellt. Schließlich wird die Simulation genutzt, um die Sensitivität der PGT-Methode auf Reichweitenänderungen zu demonstrieren. Dafür können in das Phantom Cavitäten unterschiedlicher Dicke und verschiedenen Materials eingefügt werden. Für geeignet gewählte Verteilungsparameter der simulierten PGT-Spektren wird deren detektierte Änderung mit der bekannten induzierten Reichweitenänderung ins Verhältnis gesetzt. Die so bestimmte Sensitivität ist mit früheren Ergebnissen für gemessene Spektren im Rahmen der Unsicherheiten in Übereinstimmung.

The mixed state transport properties of type-II superconductors are strongly influenced by the dynamic behavior of quantized magnetic fluxoids around the critical temperature (Tc), where a combination of normal and superconducting properties is exhibited. To understand the mixed state transport properties of type-II superconducting NbN ultrathin films (2D) we measured sheet resistance (RxxM) and Hall resistance (RxyM) of a 5-nm-thick NbN film around Tc (10.75 K) at temperatures 10.40, 10.68, and 10.77 K. Hall resistance (HR) was measured in external out-of-plane and in-plane magnetic fields up to 6 T, using 100 μA and 1 mA driving current in Van der Pauw geometry. The electric field of applied bias and Lorentz force of applied external magnetic field causes a movement of the normal conducting electrons within each fluxoid. The moving fluxoids cause dissipation and generation of Hall voltage. We developed a macroscopic analysis of the Hall resistance arising from fluxoids, to advance the differentiation between dissipating current and superconducting currents in type-II superconductors at Tc. We have extracted the number of normal conducting carriers per fluxoid and areal density and mobility of the fluxoids in dependence on the external magnetic field. This differentiation provides valuable insights into the dissipation mechanisms observed during transport measurements, e.g., after localized heating due to single photon absorption in nanostructured type-II superconductors. Furthermore, the developed macroscopic analysis of Hall resistance of fluxoids shows promising potential for investigating the fundamental aspects of fluxoid-defect interactions in type-II superconductors. © 2024 authors. Published by the American Physical Society.

Semiconductor spin qubits combine excellent quantum performance with the prospect of manufacturing quantum devices using industry-standard metal-oxide-semiconductor (MOS) processes. This applies also to ion-implanted donor spins, which further afford exceptional coherence times and large Hilbert space dimension in their nuclear spin. Here multiple strategies are demonstrated and integrated to manufacture scale-up donor-based quantum computers. 31PF_2 molecule implants are used to triple the placement certainty compared to 31P ions, while attaining 99.99% confidence in detecting the implant. Similar confidence is retained by implanting heavier atoms such as 123Sb and 209Bi, which represent high-dimensional qudits for quantum information processing, while Sb_2 molecules enable deterministic formation of closely-spaced qudits. The deterministic formation of regular arrays of donor atoms with 300 nm spacing is demonstrated, using step-and-repeat implantation through a nano aperture. These methods cover the full gamut of technological requirements for the construction of donor-based quantum computers in silicon.

A data-driven framework is presented for building spin-aware machine-learning interatomic potentials (ML-IAPs) for large-scale spin-lattice dynamics simulations. The ML-IAPs are constructed by coupling a collective atomic spin model with an ML-IAP. Together, they represent a potential energy surface from which the mechanical forces on the atoms and the precession dynamics of the atomic spins are computed. Both the atomic spin model and the ML-IAP are parametrized on data from first-principles methods - Density Functional Theory (DFT) using Spectral Neighbor Analysis Potential (SNAP) descriptors. The generated spin-aware ML-IAP can be directly used in the LAMMPS package to perform coupled spin-molecular dynamics simulations. Leveraging the framework enables performing simulations to study magnetic materials at large lengthscales and longer timescales with first-principles accuracy.

Despite its broad potential applications, substitution of carbon by transition metal atoms in graphene has so far been explored only to a limited extent. We report the realization of substitutional Mn doping of graphene to a record high atomic concentration of 0.5%, which was achieved using ultralow-energy ion implantation. By correlating the experimental data with the results of ab initio Born−Oppenheimer molecular dynamics calculations, we infer that direct substitution is the dominant mechanism of impurity incorporation. Thermal annealing in ultrahigh vacuum provides efficient removal of surface contaminants and additional implantation-induced disorder, resulting in Mn-doped graphene that, aside from the substitutional Mn impurities, is essentially as clean and defect-free as the as-grown layer. We further show that the Dirac character of graphene is preserved upon substitutional Mn doping, even in this high concentration regime, making this system ideal for studying the interaction between Dirac conduction electrons and localized magnetic moments. More generally, these results show that ultralow energy ion implantation can be used for controlled functionalization of graphene with substitutional transition-metal atoms, of relevance for a wide range of applications, from magnetism and spintronics to single-atom catalysis.

This study assesses the impact of Treated Distillate Aromatic Extract (TDAE) oil, at concentrations of 0–20 parts
per hundred rubber (phr), on the glass transition temperature (Tg) of High Vinyl/Low Styrene Styrene-Butadiene
Rubber (HVLSS-SBR), polybutadiene rubber (BR), and their blends with weight ratios of 70/30 and 50/50. Using
Dynamic Mechanical Analysis, Broadband Dielectric Spectroscopy, and Positron Annihilation Lifetime Spectroscopy,
we found that TDAE modifies Tg and fractional free volume (Fv) differently across materials. In HVLSSSBR,
TDAE reduced Tg by approximately 10 ◦C and increased Fv by 0.8 %. In BR, TDAE raised Tg by 5–7 ◦C
without altering Fv. The 70/30 blend showed no Tg change but a 0.6 % Fv increase. For the 50/50 blend, one
Havriliak-Negami equation indicated a Tg rise of 2–3 ◦C and a 0.4 % Fv increase. A two-equation analysis
revealed a 6 ◦C Tg increase and 0.9 % Fv boost in the BR-rich phase, versus a 2 ◦C rise and 0.3 % Fv uptick in the
HVLSS-SBR-rich phase. The sequence of compatibility, influenced by TDAE, is crystalline BR > amorphous BR >
HVLSS-SBR >70/30 blend >50/50 blend. This study provides valuable insights into the behavior of TDAE oil in
rubber blends and can serve as a basis for further research in this field.

The design of novel materials for various scientific and technological purposes such
as in electronics and the energy sector has in recent years benefitted from the
introduction of data-driven design strategies. Here, the power of this approach is
leveraged for two exemplary materials classes.
The recent surprising experimental realization of non-van der Waals 2D compounds
obtained from non-layered crystals [1] foreshadows a new direction in 2D systems
research. We present several dozens of candidates of this novel materials class
derived from applying data-driven research methodologies in conjunction with
autonomous ab initio calculations [2,3,4]. The candidates exhibit a wide range of
appealing electronic, optical, and magnetic properties making them an attractive
platform for fundamental and applied nanoscience.
Also high-entropy materials have recently attracted significant interest due to their
favorable properties within mechanically and thermally demanding environments.
For their actual design, predictive synthesizability descriptors such as the disordered
enthalpy-entropy descriptor (DEED) [5] are crucial prerequisites. We present an
extensive validation of the predictive power of this approach and its prospective
combination with enthalpy corrections for ionic materials [6] for the efficient
computational design of high-entropy compounds for extreme conditions.
[1] A. Puthirath Balan et al., Nat. Nanotechnol. 13, 602 (2018).
[2] R. Friedrich et al., Nano Lett. 22, 989 (2022).
[3] T. Barnowsky et al., Adv. Electron. Mater. 9, 2201112 (2023).
[4] T. Barnowsky et al., Nano Lett. 24, 3874 (2024).
[5] S. Divilov et al., Nature 625, 66 (2024).
[6] R. Friedrich et al., npj Comput. Mater. 5, 59 (2019).

The computational design of ionic materials such as ceramics relies on accurate
enthalpies. While standard electronic structure approaches based on density functional
theory can provide quantitatively accurate results for intermetallic compounds, they fail
to yield a proper description of the thermodynamics of ionic materials such as oxides as
the mean absolute errors for formation enthalpies are on the order of several hundred
meV/atom [1]. This hinders the materials design of for instance high-entropy ceramics
or lower dimensional systems such as 2D oxides.
To address this pressing issue, we have recently developed the coordination corrected
enthalpies (CCE) method based on the number of cation-anion bonds and the cation
oxidation states. This correction scheme founded on the bonding topology decreases
the prediction errors by almost an order of magnitude down to the room temperature
thermal energy scale of ~25 meV/atom for oxides, halides, and nitrides [1,2]. It is also
capable of correcting the relative stability of crystal polymorphs. The efficient
implementation of this scheme into the AFLOW framework for materials design in the
form of the AFLOW-CCE module [3] enables now the correction of enthalpies in large
materials databases as well as for the construction of convex hull phase diagrams.
These computational advances are an important enabler for the design of novel highentropy
materials. The reliable computational modelling of such systems can be
realized by the partial occupation algorithm [4] by expanding the disordered system into
a large set of ordered structures. For the actual design of these compositionally
complex disordered high-entropy systems, predictive synthesizability descriptors such
as the disordered enthalpy-entropy descriptor (DEED) [5] are crucial prerequisites. It
critically relies on the accuracy of the enthalpies of all competing phases within the
chemical space of interest as provided by the CCE method.
Literature:
[1] R. Friedrich et al., npj Comput. Mater. 2019, 5, 59. [2] R. Friedrich & S. Curtarolo, J.
Chem. Phys. 2024, 160, 042501. [3] R. Friedrich et al., Phys. Rev. Mater. 2021, 5,
043803. [4] K. Yang et al., Chem. Mater. 2016, 28, 6484. [5] S. Divilov et al., Nature
2024, 625, 66 (2024).

While 2D materials are traditionally derived from bulk layered crystals bonded by weak van
der Waals (vdW) forces, the recent surprising experimental realization of non-vdW 2D compounds
obtained from non-layered transition metal oxides [1] foreshadows a new direction in
2D systems research.
As outlined by our recent data-driven investigations [2, 3], these materials exhibit in particular
unique magnetic properties owing to the magnetic cations at the surface of the sheets. Based on
screening the AFLOW materials database first by a structural criterion for representatives similar
to the experimentally realized systems and focusing then on magnetic compounds, we obtain
12 magnetic candidates (Fig. 1a). Despite of a few ferromagnetic systems, even for the
antiferromagnetic representatives, the surface spin polarizations are diverse ranging from moderate
to large values modulated in addition by ferromagnetic and antiferromagnetic in-plane
coupling (Fig. 1b). At the same time, chemical tuning by surface passivation provides a valuable
handle to further control the magnetic properties of these novel 2D compounds and eventually
to even induce ferromagnetism as demonstrated by hydrogenation of 2D CdTiO3 [4] (Fig. 1c).
These features thus make these compounds an attractive platform for fundamental as well as
applied nanoscience and in particular spintronics.
[1] A. Puthirath Balan et al., Nat. Nanotechnol. 13, 602 (2018).
[2] R. Friedrich et al., Nano Lett. 22, 989 (2022).
[3] T. Barnowsky et al., Adv. Electron. Mater. 9, 2201112 (2023).
[4] T. Barnowsky et al., Nano Lett. 24, 3974 (2024).

Raw data and metadata related to the publication

Emitters based on photoconductive materials excited by ultrafast lasers are well-
established and popular devices for THz generation. However, so far, these emitters – both
photoconductive antennas and large area emitters - were mostly explored using driving lasers
with moderate average powers (either fiber lasers with up to hundreds of milliwatts or Ti:Sapphire
systems up to few watts). In this paper, we explore the use of high-power, MHz repetition
rate Ytterbium (Yb) based oscillator for THz emission using a microstructured large-area
photoconductive emitter, consist of semi-insulating GaAs with a 10 × 10 mm2 active area. As a
driving source, we use a frequency-doubled home-built high average power ultrafast Yb-oscillator,
delivering 22 W of average power, 115 fs pulses with 91 MHz repetition rate at a central
wavelength of 516 nm. When applying 9 W of average power (after an optical chopper with
a duty cycle of 50%) on the structure without optimized heatsinking, we obtain 65 μW THz
average power, 4 THz bandwidth; furthermore, we safely apply up to 18 W of power on the
structure without observing damage. We investigate the impact of excitation power, bias voltage,
optical fluence, and their interplay on the emitter performance and explore in detail the sources
of thermal load originating from electrical and optical power. Optical power is found to have
a more critical impact on large area photoconductive emitter saturation than electrical power,
thus optimized heatsinking will allow us to improve the conversion efficiency in the near future
towards much higher emitter power. This work paves the way towards achieving hundreds of
MHz or even GHz repetition rates, high-power THz sources based on photoconductive emitters,
that are of great interest for example for future THz imaging applications.

Analysis, optimization and uncertainty quantification of the aerodynamic behaviour of turbomachinery components is a fundamental part of the current industrial design process and requires the extensive use of compute-intensive CFD simulations. In this paper we investigate whether graph neural networks can be useful as surrogate models to accelerate the design process, for example in a multi-fidelity framework. Graph neural networks promise to provide good estimates of flow quantities while maintaining the geometric accuracy at a fraction of the computational effort of classical CFD. An application to industrially relevant turbomachinery flows is performed to gain a good understanding of the capabilities and limitations of such methods. We therefore apply a state-of-the-art graph neural network to a turbomachinery setup of industry-relevant mesh size. In particular, a multiscale graph neural network is used to overcome the problems of large information distances when applying message-passing based graph-net blocks to large meshes. The database used to train the network consists of a space-filling DoE of 100 CFD solutions with different geometries. The first use case encompasses the prediction of the flow quantities of the complete fluid domain with 2.5e6 mesh points. The second use case focuses on predicting a single scalar (e.g. pressure or temperature) on surface meshes with up to 30e3 mesh points. In both cases, the networks are employed to predict time-averaged and unsteady flow fields on unstructured meshes of variable point sizes for new geometries not present in the training set. The results demonstrate the proficiency of the approach in predicting time-averaged and unsteady flow quantities on surfaces as well as for full fluid domains for new geometries.

Microfluidic technology, especially the droplet-based format, redefined biochemical methods, enhancing detection efficiency, reducing material consumption, and enabling real-time tracking of reactors, with applications spanning biology, biotechnology, and clinical diagnosis. Gaining insight into the dynamic fluctuations of biomarker levels in patients over time holds significant value for health tracking and postoperative diagnostics, as biomarkers serve as measurable indicators providing information within an organism. For instance, α-amylase levels in drainage fluid diagnose complications, but current methods delay adjustments due to only testing on the first and third day after the operation. Our strategy employs a portable device merging droplet-based microfluidic reactors and an optical biosensor for continuous α-amylase monitoring. This enables real-time detection, notably enhances sensitivity, minimizes fluid and reagent usage, and conserves resources.
The device's adjustability allows the detection of other enzymes and metabolism products, such as lipase, lactate, etc. For example, we used our portable device to monitor the lactate concentration in animal trials, with promising results correlating well with clinical blood measurements. In our lab, we also gelation the droplet reactors as 3D cancer cell models for T cell therapy. We expect to use our innovative droplet-based reactors in broader applications in clinical diagnosis for enabling personalized clinical treatment.

Biomarkers play an important role in early detection and prognosis; evaluating and monitoring their levels can indicate various clinical conditions of diseases (e.g., cancer and metabolic disorders).1 However, the traditional diagnostic methods often involve time-consuming laboratory assays, delaying clinical decisions. In recent years, there has been a growing interest in developing portable point-of-care diagnostic tools for rapid and accurate detecting of biomarkers.2 However, these biomolecular tests mainly focus on detecting biomolecules intermittently, lacking real-time and continuous monitoring. In our group, we present a novel portable droplet-based microfluidic system, combined with optical sensors, for the real-time continuous and long-term monitoring of biomarker (amylase or lactate) levels. Based on encapsulating samples within discrete droplets, our platform integrates sample acquisition, enzymatic assays, and optical detection, enabling real-time monitoring of biomarker concentrations with minimal sample volumes, reagent dose, and processing time. Moreover, our approach can analyze diverse clinical samples, including blood, interstitial fluids, and drain liquid with high sensitivity, selectivity, and accuracy. In previous work, we have achieved real-time sensing of drain α-amylase activity of patients undergoing pancreatic surgery with a bedside portable droplet-based millifluidic device.3 This strategy significantly improves the determination time (3 min), the detection limit of 7 nmol/s·L, and minimal material requirement (ca. 10 μL) and wastes. In the latest work, the portable droplet-based strategy performed well in accurately tracking lactate levels in the blood and interstitial liquid during animal trials, which aims to locally monitor lactate levels to indicate tissue blood perfusions during skin graft surgery. In summary, the droplet-based platform used in biomarkers monitoring brings a big potential in medical diagnosis, disease monitoring, peri-, and postoperative monitoring, and metabolism tracking during exercise.
1 S. Qiuet al, Signal Transduction and Targeted Therapy 8.1 (2023): 132.
2. A. Natalia et al., Nature Reviews Bioengineering 1.7 (2023): 481-498.
3. X. Zhao et al., Biosensors and Bioelectronics 251 (2024): 116034.

Copper nanowires (Cu NWs) are popular potential building blocks of various interconnecting components, microscale circuits, and nanoelectronics. Making interconnects at the nanoscale is still an open problem, and various methods have been explored during the past decades. While ion beam joining has been known for quite some time, the beam parameter-dependent processes leading to joining is yet to be understood in detail. A low-energy (5 keV) and broad argon ion beam is unable to induce joining among the Cu NW mesh, at the low ion currents (<400 nA). However, when the ion current was elevated to 1 µA at the same energy, a large-scale joining was observed. We developed a 3D finite volume model for heat transfer and Joule heating-based melting, which successfully explains the ion current-induced joining. When the current is increased to a significantly high level, the network fragments into smaller copper nanoparticles due to the heat produced. On the other hand, at higher argon ion energy (200 keV) a large-scale joining is observed even at small (<400 nA) beam current. A state-of-the-art, Monte Carlo-based TRI3DYN simulation predicted the role of recoils, redeposition, and ion beam mixing in such joining process at high ion energy, which is mostly due to elastic collisional consequences. Such ion current-induced nanowelded copper mesh-coated PET substrate shows good transmission in the optical range of wavelengths and a notable decrease in the sheet resistance is observed.

The new generation of satellite hyperspectral (HS) sensors provides remarkable potential  for  regional-scale  mineralogical  mapping.  However,  as  with  any  satellite  sensor,  mapping  results  are  dependent  on  a  typically  complex  correction  procedure  needed  to  remove  atmospheric,  topographic  and  geometric  distortions  before  accurate  reflectance  spectra  can  be  retrieved.  These  are  typically applied by the satellite operators but use different approaches that can yield different results. In this study, we conduct a comparative analysis of PRISMA, EnMAP, and EMIT hyperspectral  satellite  data,  alongside  airborne  data  acquired  by  the  HyMap  sensor,  to  investigate  the  consistency between these datasets and their suitability for geological mapping. Two sites in Namibia  were selected for this comparison, the Marinkas-Quellen and Epembe carbonatite complexes, based  on their geological significance, relatively good exposure, arid climate and data availability. We conducted qualitative and three different quantitative comparisons of the hyperspectral data from these  sites.  These  included  correlative  comparisons  of  (1)  the  reflectance  values  across  the  visible-near  infrared (VNIR) to shortwave infrared (SWIR) spectral ranges, (2) established spectral indices sensitive to minerals we expect in each of the scenes, and (3) spectral abundances estimated using linear  unmixing. The results highlighted a notable shift in inter-sensor consistency between the VNIR and  SWIR spectral ranges, with the VNIR range being more similar between the compared sensors than  the SWIR. Our qualitative comparisons suggest that the SWIR spectra from the EnMAP and EMIT  sensors are the most interpretable (show the most distinct absorption features) but that latent features (i.e., endmember abundances) from the HyMap and PRISMA sensors are consistent with geological  variations.  We conclude  that  our  results  reinforce  the  need  for  accurate  radiometric  and  topographic  corrections,  especially  for  the  SWIR  range  most  commonly  used  for  geological  mapping.

Plant growth on mine wastes is restricted by the lack of water, nutrients, phytotoxic responses and
the absence of a seedbank. In a mesocosm study, we addressed the establishment of vegetation
on metalliferous mine wastes from two seed mixtures. Besides the composition of the vegetation
and the increase in plant cover and biomass over time, we studied concentrations of heavy metals
in the shoot and analyzed the quantity of throughflow, its pH and EC to follow pollutant discharge.
We hypothesized that the types of mine wastes and sown grasslands will affect species composition
and the formation of a protective plant cover. Our platform was well-suited to study build-up and
succession of a vegetation layer and its potential to stabilize mine wastes. However, the establishing
community was less diverse than expected. The dilution of wastes increased species number and
biomass, and we found a reduction of material discharge with increasing vegetation cover. Over
time, drainage was reduced, while pH of the throughflow did not change. However, it was higher
under the addition of greywater. Interestingly, the use of greywater led to a higher biomass in one
mixture and slight changes in the chemistry of the throughflow and the plant matter.

Two series of Th1-xZrxSiO4 phases were synthesized hydrothermally under weakly basic (pH = 8) and strongly acidic (pH = 1) conditions. Changes in pH were found to have a significant effect on experimental phase diagrams. Synthesis at pH = 8 favors the formation of Th-rich phases with resulting Th1-xZrxSiO4 solid solution for x = 0 – 0.5. Contrary, synthesis at pH = 1 results in the formation of pure end-members of the ThSiO4-ZrSiO4 pseudo-binary system separated by multiple miscibility gaps. Phases formed both under basic and acidic conditions were found to retain water, which can be discharged from the structure upon heating. A different high-pressure (HP) behaviour was found for Th-rich and Zr-rich solid solutions. While Th-rich Th0.9Zr0.1SiO4 and Th0.6Zr0.4SiO4 phases retain their stoichiometry and crystal structure upon compression at HP, a significant reduction of the Th occupancy related to a decrease of the Th-O distances is observed for the Th-poor Th0.26Zr0.74SiO4 phase at P > 8 GPa, with the subsequent formation of a Th-rich amorphous phase. The Th diffusion between the crystalline and amorphous phases was found to be fully reversible. This unique self-healing property makes these phases promising candidates for nuclear applications under extreme pressure and temperature conditions, in particular those found in underground repositories.

The dataset consists of Infrared photodissociation (IRPD) spectra of Cu+(H2O)(H2)n (with n ≤ 3) and its isotopologue measured on the Leipzig 5 K ring-electrode ion-trap triple mass spectrometer. Besides, it contains the Energy Decomposition Analysis (EDA), the benchmark results, the harmonic and the anharmonic VPT2 frequencies results as well as the script used to get the predicted separation factor for the adsorbed dihydrogen isotopologue.

Little is known about the strong mediating effect of the ligand sphere and the coordination geometry on the strength and isotopologue selectivity of hydrogen adsorption on the undercoordinated copper(I) site. Here, we explore this effect using gas-phase complexes Cu+(H2O)(H2)n (with n ≤ 3) as model systems. Cu+(H2O) attracts dihydrogen (82 kJ mol−1) more strongly than bare Cu+ (64 kJ mol−1) does. Combining experimental and computational methods, we demonstrate a high isotopologue selectivity in dihydrogen binding to Cu+(H2O), which results from a large difference in the adsorption zero-point energies (2.8 kJ mol−1 between D2 and H2, including an anharmonic contribution of 0.4 kJ mol−1). We investigate its origins and the bond strengthening between Cu+ and H2 upon addition of a single H2O ligand. We discuss the role of the environment and the coordination geometry of the adsorption site in achieving a high selectivity and the ramifications for identifying and designing future materials for adsorptive dihydrogen isotopologue separation.

Langevin dynamics simulations are used to analyze the static and dynamic properties of an XY model adapted to dimers forming on Si(001) surfaces. The numerics utilise high-performance parallel computation methods on GPUs. The static exponent ν of the symmetry-broken XY model is determined to ν=1.04. The dynamic critical exponent z is determined to z=2.13 and, together with ν, shows the behavior of the Ising universality class. For time-dependent temperatures, we observe frozen domains and compare their size distribution with predictions from Kibble-Zurek theory. We determine a significantly larger quench exponent that shows little dependence on the damping or the symmetry-breaking field.

The Helmholtz project FINEST addresses challenges in the fields of circular economy, recycling and sustainable resources. Part of this work involves the mixing of fine particles to recycle those materials, which cannot be separated further. The work includes Modelling of Powder Mixing and Segregation. Additionally, the process is studied using Microfocus X-Ray CT (μCT).
Industrial processes are inevitably associated with generating fine-grained particulate matter. Such fine-grained residues rarely find re-entry into industrial value chains; typically, they are disposed and become an environmental burden. Prominent examples are dusts from mineral processing, degraded end-
of-life fibers, or micro plastic entering the natural environment. FINEST will process different residues in an optimized manner to generate value and to minimize hazards. Economic and ecological assessment of waste management concepts provides opportunities to create value by decreased disposal costs. Associated institutions provide the capability to transfer FINEST results to the relevant industrial sectors and potential consumers. The appendant Research School educates a next generation of experts for leadership positions in industry and academia.
In powder mixing, segregation is caused by differences in particle properties. In the context of FINEST, it is by their different density, because the particles range from plastics to metals. We choose a noninvasive technique to investigate the process. Particles from 150 – 250 μm with densities between 0.5 – 5 g/cm³ are mixed in a cylindrical bladed mixer. The μCT scans of powder mixtures are acquired with voxel size of 100 μm. Using a 3D analysis method, the quality of mixture is described by a variance measure. We present the method on a few sample measurements. It describes the evolution of mixing quality over time.
Continuum modelling is chosen to simulate the mixing studied experimentally before. Discrete methods would reach their computational limits. Continuum models of powder mixing in a bladed mixer were given e.g. by Yang et al. (2022). They include size-segregation. Density driven segregation was covered in a continuum model of an annular shear cell (Tirapelle et al, 2021). We combine those approaches. First step was to implement our Finite Volume Model in OpenFOAM. It is an Eulerian model, featuring a transport equation with advection, diffusion and segregation term. Flow behavior of powders is described by μ(I)-rheology.

The recycling of fine-grained residues from various industrial sources poses challenges in terms of their processing. One processing step is the mixing of fine particles. When mixing powders, segregation can occur due to differences in particle properties. As part of a national consortium project, we are investigating the behaviour of powders with different densities, which is relevant when e.g. plastics and metals from shredding are processed together. For our study we used a non-invasive technique to investigate the mixing process: Microfocus X-ray Computed Tomography (μCT).
Particles from 150 - 250 μm with densities between 0.5 - 5 g/cm³ are mixed in a cylindrical bladed mixer. The μCT scans of the powder mixtures are taken with a voxel size of 100 μm. Using a 3D analysis method, the quality of the mixture is described by a variance measure. We discuss the method for selected experiments. It can be used to describe the evolution of mixture quality over time. When applied to a variety of mixtures, the method can be used to investigate the effects of different parameters such as mixing speed, density ratio and mixing time. This will reveal their contribution to segregation and the dependence of the variance measure (representing mixing quality).

The connection between metadata, data, and software and the integration in an overall lifecycle is crucial for effective data management in research. The generic data management lifecycle, developed at HZDR, bridges these critical components, ensuring seamless data discovery, accessibility, and reproducibility. The approach emphasises the planning of experiments, the role of metadata, data storage, as well as software versioning, and the final publication of digital research artefacts, which enables comprehensive traceability from data creation to long-term archiving. By aligning these elements in a unified procedure, we recommend a uniform lifecycle that can be adapted to different research areas, with a particular focus on photon science and community services such as SciCat that improve data integrity and promote collaborative research.

The textures of the β- and α-phases of the metastable β-titanium alloy Ti5321 after hot
deformation were investigated by neutron diffraction. A hot-rolled bar was solutionized in the
β-phase field and then hot compressed above and below the β-transus temperature. The initial texture
after full recrystallization and grain growth in the β-phase field exhibits a weak cube component
{001}<100> and minor {112}<110> and {111}<110> components. After hot compression, a <100> fiber
texture is observed, increasing in intensity with compression temperature. Below the β-transus
temperature, dynamic recrystallization of the β-phase and dynamic spheroidization of the α-phase
interact strongly. The texture of the α-phase is a <11–20> fiber texture, increasing in intensity with
decreasing compression temperature. The mechanisms of texture formation during hot compression
are discussed.

Macropa-PSMA-ligand conjugates used for targeted alpha-therapy (TAT) with actinium-225 were furnished with an albumin binder to improve their pharmacological behaviour in vivo. [1,2] Additionally, the introduction of an iodine-containing albumin binder provides the basis for the development of a novel theranostic radioconjugate pair using the radiohybrid approach. This involves the complexation of the alpha emitter actinium-225 (half-life: 9.9 d) and the introduction of the easily accessible SPECT-compatible radiohalogen iodine-123 into the same molecule. Advantageously, its ideal physical half-life of 13.2 h and mild radioiodination conditions allows the imaging of longer circulating radioconjugates. The PSMA-binding motif based on the PSMA-617 structure was prepared by a multi-step peptide synthesis followed by subsequent conjugation with the macropa chelator by Cu-catalysed azide-alkyne (CuAAC) click chemistry. The labelling precursor for the introduction of iodine-123 was synthesized by replacing the 4-(p-iodophenyl)butyrate by a trimethylstannyl group to enable labelling by electrophilic aromatic substitution reaction. To determine the binding affinity, LNCaP cells were incubated with the nonradioactive conjugates (with and without nonradioactive lanthanum (La) as congener for actinium-225) in a competition assay and spiked with the radioconjugate [133La]La-PSMA-617. The influence of the complexing agent and the metal ion loading on the binding affinity was evaluated. Two radioconjugates were developed: [123I]I-mcp-M-alb-PSMA with one PSMA-binding motif was prepared from the stannyl precursor (DMSO, Iodogen, 20 min, rt, RCY: 49%) and [123I]I-mcp-D-alb-PSMA with two PSMA-binding motifs was labelled under the same conditions with the exception of adding nonradioactive iodine after completion of radiolabelling to iodinate the second stannyl group (RCY: 20%). Both radioconjugates were purified by HPLC. Beneficially, no influence of chelator loading on cell binding was observed in vitro. The cell binding is comparable across the analogues (mcp-M-alb-PSMA: Ki = 8.46 nM (7.05 - 10.14), La-mcp-M-alb-PSMA: Ki = 8.46 nM (6.72 - 10.66) / mcp-D-alb-PSMA: Ki = 2.35 nM (2.03 - 2.71), La-mcp-D-alb-PSMA: Ki = 2.21 nM (1.64 - 2.96)). Preliminary small animal SPECT imaging with tumor-bearing mice was executed pointing out a biodistribution of [123I]I-mcp-M-alb-PSMA which is comparable to [225Ac]Ac-mcp-M-alb-PSMA. The synthesis of the tin precursors and subsequent radiolabelling with iodine-123 provided two new radioconjugates which act as diagnostic counterparts to the corresponding actinium-225 radioconjugates. The introduction of iodine-123, with or without metal ion loading of the macropa chelator, did not alter the PSMA binding affinity in vitro. The addition of the albumin binding domain opens up a new approach to use iodine-123 in combination with actinium-225 as new radiohybrid pair for the development of hybrid radiopharmaceuticals within the theranostic concept.

Gas evolution at surfaces occurs in a multitude of industrial processes and is a complex phenomenon. A wide range of length scales is involved from nucleation to bubble departure. The evolution of gas bubbles depends on the specific wetting dynamics at the surface and the local conditions like species distribution, temperature, pressure or outer flow. Advancing the bubble growth and gas transport in electrochemical electrolyzers for producing hydrogen can be expected to be beneficial with respect to the overall efficiency of the device.
The presentation will show detailed results of the gas evolution at surfaces of different morphology and surface in order to improve our knowledge how the gas transport can be improved. The results are based on numerical simulations by a VOF method and a mass transfer model that correctly accounts for the flux of dissolved gas into the bubble. Hereby, different wetting dynamics are considered to elaborate the surface influence. The results will further be compared with experimental results available in our group and from literature.

Dinuclear metal complexes present a well-known substance class in the chemistry of the transition metals with a wide variety of applications. However, for the 5f elements, the actinides, such complexes are still rare, with a focus on uranium complexes for the activation of small molecules. Due to their interesting electronic properties, however, the actinides differ greatly from other metals in the periodic table, and the possibility of having two of these metal ions in close proximity in a well-defined molecular framework might provide fascinating insights into the fundamental properties of these elements. The rigid, ambidentate phthalimidinyl anion is a promising ligand for the synthesis of bimetallic complexes
The synthesis of such bimetallic actinide complexes can be achieved by reacting the respective actinide tetrachlorides, UCl₄, [ThCl₄(DME)₂], [NpCl₄(DME)₂], and [PuCl₄(DME)₂] (DME = 1,2-dimethoxyethane), with the antimony compound phenyldi(phthalimidinyl)antimony. The antimony reagent bears two advantages over common salt metatheses reactions. 1) The Sb–N bond is quite weak resulting in an easy transfer of the phthalimidinyl ligand to the actinide, and 2) antimony is a highly chlorophilic element that can abstract the chloride ions from the actinide salts to form soluble antimony chloride compounds such as PhSbCl₂. The synthesis was carried out in the coordinating solvent pyridine which leads to the formation of well-defined dinuclear species by saturating the coordination sphere of the metals and prevents the formation of polymeric species. The compounds crystallize readily from the reaction solution in pyridine after standing for a few days in a nitrogen-filled glovebox.
This easy synthetic route proved to be effective for a series of tetravalent actinides, enabling the preparation of an isostructural series ranging from thorium to plutonium. The comparably close proximity (i.e. ~4.65 Å) of the two paramagnetic metal ions (in case of U, Np and Pu) lends itself to investigations of their magnetic coupling behavior with interesting effects detectable by paramagnetic NMR as well as SQUID magnetometry. Additionally, the determined crystal structures allow for the computational characterization of the compounds including calculated pseudocontact shift (PCS) fields that support the interpretation of paramagnetic shifts in NMR spectroscopy. Due to the close proximity of the metal atoms, the individual PCS cones merge, potentially leading to interesting effects on the NMR spectra of the complexes.
We will discuss structures in solid and solution as well as magnetic and bond properties of these novel bimetallic actinide compounds.

The process of electrolysis at microelectrodes in acidic solutions allows the detailed study of the dynamics of single hydrogen bubbles from nucleation to growth until detachment from the electrode. In earlier work, we have identified three different growth regimes of single hydrogen bubbles that occur depending on the potential applied and the electrolyte concentration [1]. At the bubble interface, a thermal Marangoni flow exists, and the hydrogen bubble may exhibit periodic oscillations or steady growth due to the varying influence of buoyancy, electric and surface tension force [2,3].
Although the thermocapillary effect during bubble growth at microelectrodes is well recognized, the interfacial flow velocity measured decays faster than found in the first simulation results of Massing et al. [4]. This might be caused by the presence of tracer particles in the electrolyte used for the flow measurements, which has been overlooked so far [5]. Our recent experimental findings underscore that variations in the concentration of tracer particles exert notable changes on both the shape and dynamics of bubbles, as well as the flow patterns of the nearby electrolyte. In the steady growth regime, the current and departure time are slightly increased when the particle volume concentration is increased, but the contact radius is reduced. In the oscillatory regime, the oscillating frequency, departure time and current all decrease with the increase in particle volume concentration.
Consequently, we propose a theoretical model elaborating the attraction of charged particles to the bubble interface and the resulting modification of the dynamics of the particle laden interface and the bubble [6]. This model enables quantitative corrections for the measurement and simulation deviations. The numerical simulations are conducted using COMSOL, revealing a good agreement in the tangential velocity profile at the bubble interface arising from both thermo- and soluto-capillary effects (see Figure 1). The oscillatory motion of a hydrogen bubble on the electrode is also simulated. Furthermore, the force balance on the bubble is studied in detail, which provides a deeper insight into the complex phenomena of electrolytic gas evolution.

Electrochemical gas evolution at electrodes beside mass transfer across the interface involves a variety of phenomena at different scales that are coupled with each other. Today, our understanding still seems to be limited, e.g. with respect of accurately predicting the bubble departure size. As the details of growth and transport of gas bubbles have a strong impact on the performance of electrolyzer devices, a better understanding is needed for improving their efficiency. The talk will elaborate on recent progress in understanding how capillary, thermal, electric and wetting effects influence the gas bubble evolution, thereby combining experimental and numerical efforts.

In this work, we developed a direct strategy to fabricate Palladene (i. e. Palladium metallene) aerogels and propose a temperature-dependent growth mechanism. Besides the typical three-dimensional networks and wrinkled surface morphologies, the as-prepared Palladene₅₀ aerogel is endowed with abundant Pd²⁺. The as-prepared Palladene₅₀ aerogel exhibits an excellent mass activity in the formic acid oxidation reaction and a good half-wave potential in the oxygen reduction reaction in comparison with Pd/C and a Pd aerogel. This work expands the range of metal aerogels from the perspective of the building block units and demonstrates a direct approach to fabricate highly promising bifunctional electrocatalysts for fuel cells.

Nitrilotris(methylenephenylphosphinic) acid (NTPAH₃) was silylated using hexamethyldisilazane to produce the tris(trimethylsilyl) derivative NTPA(SiMe₃)₃. From the latter, upon alcoholysis in chloroform, NTPAH₃ could be recovered. Thus, a new modification of that phosphinic acid formed. Meanwhile, NTPAH₃ synthesized in aqueous hydrochloric acid crystallized in the space group P3c1 with the formation of O-H···O H-bonded networks (NTPAH₃P), in chloroform crystals in the space group R3c formed (NTPAH₃M), the constituents of which are individual molecules with exclusively intramolecular O-H···O hydrogen bonds. Both solids, NTPAH₃P and NTPAH₃M, were characterized by single-crystal X-ray diffraction, multi-nuclear (¹H, ¹³C, ³¹P) solid-state NMR spectroscopy, and IR spectroscopy as well as quantum chemical calculations (both of their individual constituents as isolated molecules as well as in the periodic crystal environment). In spite of the different stabilities of their constituting molecular conformers, the different crystal packing interactions rendered the modifications of NTPAH₃P and NTPAH₃M similarly stable. In both solids, the protons of the acid are engaged in cyclic (O=P–O–H)₃ H-bond trimers. Thus, the trialkylamine N atom of this compound is not protonated. IR and ¹H NMR spectroscopy of these solids indicated stronger H-bonds in the (O=P–O–H)₃ H-bond trimers of NTPAH₃M over those in NTPAH₃P.

The exploration of the coordination chemistry of actinides significantly lags behind that of transition metals as well as their lanthanide homologues. As such, a fundamental understanding of the binding properties in actinide compounds is still leaving many open questions. Therefore, systematic investigation of various coordination motives around an actinide centre can be used as benchmark to evaluate what analytic techniques can reveal about novel actinide-ligand bonding.
In this study, we focus on a square antiprism coordination of only oxygen donor atoms in an actinide series ranging from thorium to plutonium. Installing either one or two transition metals in close proximity to the actinide, leads to an 8+2 coordination at the actinide centre. These heterobi- and trimetallic complexes have been investigated using single-crystal X-ray diffraction, NMR, HERFD-XANES, and SQUID magnetometry. The experimental findings were further analysed with quantum chemical calculations. A comparison with their monometallic counterparts gives new insight into actinide-transition metal bonding.

The 2-pyridyloxy ligand (PyO−) has proven to be a useful ligand to isolate heterobimetallic complexes and thus supporting bonds between transition metals (TM) and/or main-group elements. Although interesting coordination motifs can be expected especially with actinides, metal-metal interactions remain a scarce phenomenon in actinide chemistry. Together with the high coordination numbers and various oxidation states, actinide 2-hydroxypyridinolate complexes would have the necessary flexibility to form a variety of actinide complexes also containing a transition metal.
Initially, treatment of tetravalent [AnCl₄(THF)₃] (An = Th, U, Np, Pu) with excess 2-hydroxypyridine gave a series of heteroleptic 2(1H)-pyridinone actinide complexes [AnCl(HPyO)₇]Cl₃. These complexes were good candidates to synthesise heterobimetallic complexes by the addition of [TMCl₂(THT)₂] (TM = Pd, Pt; THT = tetrahydrothiophene) and Et₃N as a supporting base. Using this synthesis method, a series of eight complexes of the type [TM(µ-PyO)₄An(µ-PyO)₄TM] (An = Th, U, Np, Pu; TM = Pd, Pt) could be isolated. These complexes have been investigated using single-crystal X-ray diffraction, NMR, HERFD-XANES spectroscopy, and SQUID magnetometry. The experimental findings were supported by quantum chemical calculations. The obtained data allows us to draw comparisons along the tetravalent actinide series and between palladium and platinum, whereby an unexpected trend in An-TM bonding has been observed.

Ultra-intense lasers that ionize atoms and accelerate electrons in solids to near the speed of light can lead
to kinetic instabilities that alter the laser absorption and subsequent electron transport, isochoric heating, and
ion acceleration. These instabilities can be difficult to characterize, but X-ray scattering at keV photon energies
allows for their visualization with femtosecond temporal resolution on the few nanometer mesoscale. Here, we
perform such experiment on laser-driven flat silicon membranes that shows the development of structure with a
dominant scale of 60 nm in the plane of the laser axis and laser polarization, and 95 nm in the vertical direction
with a growth rate faster than 0.1 fs−1 . Combining the XFEL experiments with simulations provides a complete
picture of the structural evolution of ultra-fast laser-induced plasma density development, indicating the excita-
tion of plasmons and a filamentation instability. Particle-in-cell simulations confirm that these signals are due
to an oblique two-stream filamentation instability. These findings provide new insight into ultra-fast instability
and heating processes in solids under extreme conditions at the nanometer level with possible implications for
laser particle acceleration, inertial confinement fusion, and laboratory astrophysics.

Nanostructured silicon can reduce reflectance loss in optoelectronic applications, but intrinsic silicon cannot absorb photons with energy below its 1.1 eV bandgap. However, incorporating a high concentration of dopants, i.e., hyperdoping, to nanostructured silicon is expected to bring broadband absorption ranging from UV to short-wavelength IR (SWIR, <2500 nm). In this work, we prepare nanostructured silicon using cryogenic plasma etching, which is then hyperdoped with selenium (Se) through ion implantation. Besides sub-bandgap absorption, ion implantation forms crystal damage, which can be recovered through flash lamp annealing. We study crystal damage and broadband (250–2500 nm) absorption from planar and nanostructured surfaces. We first show that nanostructures survive ion implantation hyperdoping and flash lamp annealing under optimized conditions. Secondly, we demonstrate that nanostructured silicon has a 15% higher sub-bandgap absorption (1100–2500 nm) compared to its non-hyperdoped nanostructure counterpart while maintaining 97% above-bandgap absorption (250–1100 nm). Lastly, we simulate the sub-bandgap absorption of hyperdoped Si nanostructures in a 2D model using the finite element method. Simulation results show that the sub-bandgap absorption is mainly limited by the thickness of the hyperdoped layer rather than the height of nanostructures.

Two-dimensional (2D) van der Waals heterostructures that embody the electronic characteristics of each constituent material have found extensive applications. Alloy engineering further enables the modulation of the electronic properties in these structures. Consequently, we envisage the construction and modulation of composition-dependent antiambipolar transistors (AATs) using van der Waals heterostructures and alloy engineering to advance multivalued inverters. In this work, we calculate the electron structures of SnSe2(1–x)S2x alloys and determine the energy band alignment between SnSe2(1–x)S2x and 2H-MoTe2. We present a series of vertical AATs based on the SnSe2(1–x)S2x/MoTe2 type-III van der Waals heterostructure. These transistors exhibit composition-dependent antiambipolar characteristics through the van der Waals heterostructure, except for the SnSe2/MoTe2 transistor. The peak current (Ipeak) decreases from 43 nA (x = 0.25) to 0.8 nA (x = 1) at Vds = −2 V, while the peak-to-valley current ratio (PVR) increases from 4.5 (x = 0.25) to 6.7 × 103 (x = 1) with a work window ranging from 30 to 47 V. Ultimately, we successfully apply several specific SnSe2(1–x)S2x/MoTe2 devices in binary and ternary logic inverters. Our results underscore the efficacy of alloy engineering in modulating the characteristics of AATs, offering a promising strategy for the development of multivalued logic devices.

Fe-Cr alloys serve as model alloys for the investigation of radiation induced effects in ferritic-martensitic steels which are candidate structural materials for future fusion reactors. In this work the effect of Cr segregation and/ or agglomeration in 490 keV Fe+ ion irradiated Fe-10at%Cr alloys in the form of thin films is investigated. The irradiations took place at 300 ◦C at doses ranging from 0.5 to 20 displacements per atom (dpa). Polarized Neutron Reflectivity (PNR) measurements were used for the determination of the solute Cr concentration in the Fe-Cr matrix. Cr depletion from the Fe-Cr matrix up to 2.4 at% was found. This is related to solute Cr decrement as the accumulated dose increases. After the damage of 4 dpa, solute Cr reaches the asymptotic value of 8.4 at%, close to that of the thermodynamic equilibrium in Fe-Cr. Atom Probe Tomography (APT) measurements showed that after irradiation Cr accumulates into clusters the majority of which is co-located with oxygen.

The factors that influence the formation of helium blisters in copper were studied, including crystallographic grain orientation and thermomechanical conditions. Helium implantation experiments were conducted at 40 KeV with a dose of 5 × 10¹⁷ ions/cm², and the samples were then subjected to post-implantation heat treatments at 450 °C for different holding times. A scanning electron microscope (SEM) equipped with an electron backscatter diffraction (EBSD) detector was used to analyze the samples, revealing that the degree of blistering erosion and its evolution with time varied with the crystallographic plane of the free surface in different ways in annealed and cold rolled copper. Out of the investigated states, rolled copper with a (111) free surface had superior helium blistering durability. This is explained by the consideration of the multivariable situation, including the role of dislocations and vacancies. For future plasma-facing component (PFC) candidate material, similar research should be conducted in order to find the optimal combination of material properties for helium blistering durability. In the case of Cu selection as a PFC, the two practical approaches to obtain the preferred (111) orientation are cold rolling and thin layer technologies.

Hyperdoped germanium (Ge) has demonstrated increased sub-bandgap absorption, offering potential applications in the short-wavelength-infrared spectrum (1.0–3.0 μm). This study employs ion implantation to introduce a high concentration of selenium (Se) into Ge and investigates the effects of post-implantation annealing techniques on the recovery of implantation damage and alterations in optical properties. We identify optimal conditions for two distinct annealing techniques: rapid thermal annealing (RTA) at a temperature of 650 °C and ultrafast laser heating (ULH) at a fluence of 6 mJ/cm2. The optimized ULH process outperforms the RTA method in preserving high doping profiles and achieving a fourfold increase in sub-bandgap absorption. However, RTA leads to regrowth of single crystalline Ge, while ULH most likely leads to polycrystalline Ge. The study offers valuable insights into the hyperdoping processes in Ge for the development of advanced optoelectronic devices.

Recently, both large language models and large vision models (LVMs) have gained significant attention. Trained on large-scale datasets, these large models have showcased remarkable capabilities across various research domains. To enhance the accuracy of remote sensing (RS) scene classification, LVM-based methods are explored in this letter. Due to the differences between RS images and natural images, simply transferring LVMs to RS tasks is impractical. Therefore, we conducted research on relevant techniques and appended learnable prompt tokens to the input tokens while freezing the backbone weights, reducing the parameter scale and making the LVM weights easier to harness and to transfer. In consideration of latent catastrophic forgetting issues induced by ordinary finetuning techniques and the inherent complexity and redundancy of RS images, we introduced soft adaption mechanisms between backbone layers based on prompt tuning technique and implemented the first LVM tuning method, namely, the Large Vision Model Soft Adaption for RS scene classification (LVM-StARS)-Deep and the LVM-StARS-Shallow to make LVMs more suitable for RS scene classification tasks. The proposed methods are evaluated on two popular RS scene classification datasets, and the experimental results indicate that the proposed method outperforms other state-of-the-art methods. The experimental results demonstrate that our proposed method enhances overall accuracy (OA) by 1.71%–3.94%, while updating only 0.1%–0.5% of the parameters compared to full finetuning. Furthermore, our method outperforms the existing methods.

We present an atomically precise technique to create sulfur vacancies and control their atomic configurations in single-layer MoS2. It involves adsorbed Fe atoms and the tip of a scanning tunneling microscope, which enables single sulfur removal from the top sulfur layer at the initial position of Fe. Using scanning tunneling spectroscopy, we show that the STM tip can also induce two Jahn-Teller distorted states with reduced orbital symmetry in the sulfur vacancies. Density functional theory calculations rationalize our experimental results. Additionally, we provide evidence for molecule-like hybrid orbitals in artificially created sulfur vacancy dimers, which illustrates the potential of our technique for the development of extended defect lattices and tailored electronic band structures.

Subcooled nucleate flow boiling encompasses intricate simultaneous condensation and evaporation processes. It involves thin liquid microlayers trapped beneath growing bubbles, enabling high heat and mass transfer with fluxes exceeding 1MW/m². Understanding microlayer contribution to bubble growth is pivotal for developing reliable boiling models. Unlike previous studies, we account for condensation effects, important in the context of subcooled boiling
regime, in estimating microlayer contribution by simultaneously obtaining microlayer dynamics from thin-film interferometry and whole-field temperature from rainbow schlieren deflectometry. We establish that the microlayer evaporation significantly influences bubble growth in flow boiling, contributing up to 60% in the present study.

Advancements in Earth observation technologies have greatly enhanced the potential of integrating hyperspectral (HS) images with Light Detection and Ranging (LiDAR) data for land use and land cover classification. Despite this, most existing methods primarily focus on employing deep network layers to extract features from two heterogeneous data modalities, often overlooking a gradual modeling data representation approach from shallow to deep layers. Furthermore, excessive network layers can result in the deterioration of modality-specific features, therefore lowering the classification performance. The paper proposed a novel cross-modal feature aggregation and enhancement network for the joint classification of HSI and LiDAR data. Initially, a cross-modal feature fusion module is developed to exploit spatial scale consistency to complete the interchange and fusion of feature embedding at the pixel level, preserving the original information from the two heterogeneous modalities to a certain degree. Then two straightforward strategies (i.e., addition and concatenation) are employed in the shallow network layers before being sent to the transformer encoder. The former facilitates the model’s ability to discern more subtle distinctions and refine spatial location details. The latter ensures the preservation of information integrity, effectively mitigating the risk of feature loss. Moreover, invertible neural networks and a feature enhancement module are introduced, leveraging the complementary information of HSI and LiDAR data to enhance the detail and texture information extracted in deeper layers. Extensive experiments on Houston2013, Trento, and MUUFL datasets demonstrate that the proposed method outperforms several state-of-the-art models in three evaluation metrics, achieving an accuracy improvement of up to 2%. The proposed model brings new inspirations for HSI and LiDAR classification, which is critical for accurate environmental monitoring, urban planning, and precision agriculture. The source code is publicly accessible at
https://github.com/zhangyiyan001/CMFAEN
.

Electric fields operating at THz frequencies hold significant promise for inducing ultrafast coherent excitations in magnetic heterostructures. Through the utilization of ferromagnetic/heavy metal (FM/HM) heterostructures, we have demonstrated that THz radiation (0.1 – 30 THz) exhibits combined functionality of microwaves and visible light. 1) Similar to microwaves, THz fields can effectively generate spin currents through the spin-Hall effect (SHE), resulting in an excitation of THz-frequency magnon modes. 2) Akin to visible light excitation, THz fields deposit heat, leading to the demagnetization of FM layers. Harnessing the THz-induced demagnetization as a spin current source within FM/HM heterostructures, we exploit the half-cycle THz electric field to incite spin currents, which subsequently transformed into picosecond charge currents through the inverse SHE within the HM layer. This conversion process results in the emission of a THz second harmonic signal, offering the THz spintronic frequency conversion.

We will present our ongoing efforts to support physics research with
machine learning at HZDR. We will summarize our academic efforts in our
Young Investigator Group as well as the projects handled by our
consultant team. In this manner, we will highlight our approach to ML
based research and support at HZDR as well as the Helmholtz association
in Germany. In detail, our YIG is working on surrogate models for laser
and plasma physics problems, like laser wakefield acceleration,
providing fast estimates experimental or computational results to guide
parameter optimization or accelerate inverse parameter estimation and
ML-based approaches to solve inverse phase problems. In addition to this
aspects of trustworthiness and uncertainty play a key role in our work,
which are a specialty of our consultants team, also in connection with
further topics like segmentation and natural language processing.

Overview of needs and status of near real-time adaptive particle therapy

In this overview talk the following questions will be addressed:

-What is the status concerning fast adaptions in particle therapy also in relation to photon therapy?
-Why we need online-adaptive particle therapy (OAPT)?
-What are different approaches also in relation to different adaption speed?
-What are the different imaging approaches for OAPT?
-How can we verify the treatment delivery when no pre-treatment phantom QA is performed?
-What is the role of I-based decision support?
-What initiatives exist on national and international level? Where do we stand?

The fundamental understanding of the proton transport mechanism through graphene-based proton exchange membranes (PEMs) is crucial to develop novel and advanced two-dimensional (2D) separation materials for energy conversion devices. [1] We computationally investigate ways to enhance the balance between proton permeability and selectivity using a combination of ReaxFF molecular dynamics (ReaxFF-MD), Density Functional Theory (DFT), and metadynamics. In both the cases of graphene nanopore and pristine graphene, covalent benzenesulfonic functionalization introduces significant improvements in proton permeability and selectivity compared to other moieties. [2,3] For the graphene nanopore scenario, the benzenesulfonic functionality dynamically acts as a proton trap and proton shuttle by establishing a favourable hydrogen-bond network, resulting in an effective proton channel through the nanopore (Figure 1a). [2] In the pristine graphene case, the benzenesulfonic functionality guides the proton hopping toward the distorted basal plane, enabling successive proton tunnelling to the other side of the graphene monolayer (Figure 1b). [3,4] Notably, in these systems we achieve estimated proton diffusion coefficients that are comparable to or higher than the current state-of-the-art PEM, Nafion. [2,3] The mechanisms exhibited by these benzenesulfonic functionalized graphene-based systems set the ground for designing new 2D-PEMs with efficient unidirectional proton transport features.

References

[1] Liu, X. et al. Nat. Nanotechnol. 15, 307–312 (2020).
[2] Calvani, D. et al. J. Phys. Chem. C. 128, 8, 3514–3524 (2024).
[3] Zhang, W. et al. arXiv:2308.16112.
[4] An, Y. et al. Adv. Mater. 32 (37), 2002442 (2020).

Dual energy/spectral CT

CT for RTP*: technical requirements and QA guidlines

X-ray computed tomography (CT) is the clinical standard for treatment planning in particle therapy. In this chapter, the basic principles of this state-of-the-art image modality will be described, as well as strategies to account for uncertainties of the conversion from CT number to ion stopping power.

I will introduce the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) with its two accelerator-based THz sources, FELBE and TELBE [1]. Then I will discuss two examples of nonlinear spectroscopy of excitons: the first one is the observation of the Autler-Townes splitting of an intra-excitonic 1s-2p transition in InGaAs quantum wells, an experiment more than a decade old, but still one of my favorites [2]. The second deals with the very recent observation of the THz induced photodetachment of trions in the 2D material MoSe2, i.e. the conversion of a trion (a charged exciton) into an exciton plus an electron [3]. Finally I will discuss the shortcomings of our present THz facilities, leading to the ideas for a successor facility, the Dresden Advanced Light Infrastructure DALI.

[1] M. Helm et al., Eur. Phys. J. Plus 138, 158 (2023).
[2] M. Wagner et al., Phys. Rev. Lett. 105, 167401 (2010); M. Teich et al., New J. Phys. 15, 065007 (2013); M. Teich et al., Phys. Rev. B 89, 115311 (2014).
[3] T. Venanzi et al., Nature Photonics, accepted for publication (2024).

A personal journey through four decades of THz sources, or how I didn’t invent the QCL

The ESFR SMART project, which took place from 2017 to 2022, made it possible to define a Sodium Fast Reactor (SFR) design based on past SFR experimental feedbacks and intended to meet post-Fukushima safety criteria. The main options retained are recalled here: a heterogeneous core with low sodium void reactivity effect and mitigation measures (corium transfer tubes), a sodiumresistant pit well, a metallic thick slab, and finally comprehensive set of measures allowing decay heat removal by natural convection. These studies were carried out during this project with a power of 3600 MWth which was the power of the initial EFR project initiated during the operation of Superphenix. The new ESFR-SIMPLE project, starting at the end of 2022, uses the same technical options but with reduced power. This choice could more easily allow the construction of a SFR prototype in Europe. Design options were chosen so that the reactor could be assembled off-site, then shipped by rail or ship to the construction site, which requires a vessel diameter limit of around 10 m. The paper presents the first design studies with a particular attention to the core and primary circuit sizing. The proposed ESFR-SMR results in a 360 MWth reactor. This power reduction may also allow some simplifications compared to the initial high-power concept, particularly in terms of passive evacuation of residual power. This last point will be more deeply investigated by the ESFRSIMPLE project in the next years

The current ESFR (European Sodium Fast Reactor) design was proposed and in-depth evaluated in the frame of the past ESFR-SMART project. As a follow-up project, the ESFRSIMPLE has been launched with the aim of challenging the current commercial-size ESFR design in terms of safety features and economic performance. Among the new safety measures to be developed and assessed in ESFR-SIMPLE, the current oxide fuel ESFR design will be challenged by a modified version of the core with metallic fuel. This intends to conclude on what types of benefits can be obtained with high-density fuel, under similar safety and design constraints. In this paper, the designing approach for enabling the use of metallic fuel in the current ESFR core is described and a preliminary neutronic evaluation is carried out. The optimal configuration is established through the optimization of key neutronic parameters aiming at the potential reduction of the plutonium inventory. The resulting core configuration serves as a basis for further safety assessment analyses, which will provide insight into the advantages and drawbacks of the two types of fuels.

This repository contains the modules developed as part of Data Science Education Community of Practice program of the American Physical Society. These open source modules are to be used for incorporating machine learning/data science concepts in undergraduate physics curriculum.