Contact

Porträt Prof. Dr. Kvashnina, Kristina; FWOS

Prof. Dr. Kristina Kvashnina

Head of the Synchrotron Science Department
Responsible for the BM20 (ROBL) beamline at ESRF
k.kvashnina@hzdr.de
Phone: +33 476 88 2367

Department of Synchrotron Science

Molecular Structures

Research

The Department of Molecular Structures conducts synchrotron-based research, offering a robust toolkit for scientists investigating materials containing actinides and lanthanides.

Experiments take place at the Rossendorf Beamline of The European Synchrotron (ESRF), in Grenoble (France) which is specifically dedicated to the actinide science and research on radioactive waste disposal. The beamline consists of four experimental stations -XAFS, XES, XRD-1, XRD-2:

  • XAFS station with fluorescence and transmission detection for X-ray Absorption Fine-Structure (XAFS) spectroscopy, including (conventional) X-ray Absorption Near-Edge Structure (XANES) and Extended X-ray absorption fine-structure (EXAFS) spectroscopies
  • XES with a 5-crystal Johann-type spectrometer for high-energy-resolution fluorescence-detection X-ray absorption near-edge spectroscopy (HERFD-XANES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) measurements.
  • XRD-1 station with a heavy-duty, Eulerian cradle, 6-circle goniometer for (high-resolution) powder X-ray diffraction (PXRD), surface-sensitive crystal truncation rod (CTR) and resonant anomalous X-ray reflectivity (RAXR) measurements
  • XRD-2 station with a Pilatus3 x2M detector stage for single crystal X-ray diffraction (SCXRD) and in situ/in-operando PXRD measurements.

Our research provides detailed insights into the structural and electronic properties of actinide and lanthanide-containing materials across various scientific disciplines, including physics, chemistry, environmental science, and geoscience. We study fundamental electron interactions, bonding properties, probing the local structures and oxidation states of complex systems. Data analysis is performed with the help of electronic structure calculations. 

EXAFS, HERFD-XANES, XES and RIXS is not restricted to crystalline solids, but can be applied to a wide range of samples, to derive information on e.g. aqueous speciation, complexation with dissolved inorganic ligands like chloride, sulfate or nitrate, complexation with organic ligands like acetate or humic acid, interaction with bacteria and plants, sorption to mineral and rock surfaces for actinides an other metals and metalloids. Due to the high penetration depth of the employed hard X-rays, the methods are suited to study chemical reactions in-situ/in-operando, for instance at very low or high temperatures, under special atmospheres, or under electrochemical potentials.

More about Rossendorf Beamline

Latest publication

Incorporation Mechanism of Tc(IV) in Magnetite Revealed by EXAFS Measurements and Ab Initio Simulations

Katheras, A. S.; Krack, M.; Zimmermann, T.; Scheinost, A.; Churakov, S. V.

Abstract

The reductive immobilization of Tc, a long-lived fission product present in nuclear waste, is an important geochemical mechanism regarding Tc transport in the repository near-field. Based on the ionic radius and similarity in charge, Tc(IV) is expected to substitute for Fe(II,III) in octahedral positions in magnetite, a common iron oxide. Several mechanisms have been proposed in the past for how the necessary charge compensation for the aliovalent cation substitution is obtained. In this study, we developed a reliable computational approach based on density functional theory to investigate the Tc-magnetite interaction. By comparing our simulation results to spectroscopic data, we can confirm a preference for the incorporation mechanisms, including the formation of a vacancy. For both the magnetite bulk structure as well as its commonly observed (111) surface, these findings are based on structural information and thermodynamic considerations. Our results are in line with the experimentally observed topotactic transition of the magnetite crystal structure toward the more oxidized iron mineral maghemite and reflect a component in long-term geochemical mineral transformations.

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-43061

More publications

Team

Head

NameBld./Office+49 351 260Email
Prof. Dr. Kristina KvashninaROBL/21.6.04+33 476 88 2367
k.kvashnina@hzdr.de

Employees

NameBld./Office+49 351 260Email
Dr. Lucia AmidaniROBL/14.1.04+33 476 88 1982
Dr. Nils BaumannROBL/21.6.03+33 476 88 2849
Clara Lisa E SilvaROBL/14.1.04+33 476 88 2044
Jörg ExnerROBL/BM20+33 476 88 2372
Dr. Christoph HennigROBL/21.6.02a+33 476 88 2005
Dr. Eleanor Sophia Lawrence BrightROBL/14.1.03+33 476 88 2462
Dr. Damien PrieurROBL/21.6.03+33 476 88 2463
Dr. André Roßberg801/P3162758
Anne ThielenROBL/21.6.02a+33 476 88 2232
a.thielenAthzdr.de
Dr. Sami Juhani VasalaROBL/14.1.01s.vasalaAthzdr.de