Contact

Porträt Prof. Dr. Kvashnina, Kristina; FWOS

Prof. Dr. Kristina Kvashnina

Head of Department "Molecular Structures"
Responsible for the BM20 (ROBL) beamline at ESRF

Phone: +33 476 88 2367

Department of Molecular Structures

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

High-resolution and high-pressure x-ray diffraction study of ScFe2Hx compounds

El Bidaoui, S.; Diop, L.; Svitlyk, V.; Hennig, C.; Isnard, O.

Abstract

Using synchrotron-based x-ray diffraction (SXRD), the evolution of the crystal lattice in ScFe2Hx compounds is investigated at room temperature and under pressures up to 25 GPa. High-resolution SXRD experiments reveal that the C14 hexagonal MgZn2-type structure of the parent intermetallic compound ScFe2 is preserved upon H insertion into the crystal structure in spite of the large unit-cell expansion of 21.4%. The lattice expansion proves anisotropic with a larger expansion within the basal plane of the hexagonal structure Δa/a = 7.1% against Δc/c = 5.8%. This huge increase in the cell volume is equivalent to 2.92 Å3/inserted hydrogen atom, a value much larger than that reported for several Fe-rich alloys. Angle-dispersive SXRD measurements under external pressure indicate that the hexagonal symmetry of the crystalline lattice remains unaltered within the studied compression range. No signature of a structural phase transformation has been observed at least up to the highest applied pressure. The application of hydrostatic pressure induces a monotonous contraction of the cell dimensions. A bulk modulus of K0 = 143 GPa has been inferred from the pressure-volume relationship for the initial alloy ScFe2. It is further shown that hydrogen absorption leads to a diminution of the bulk modulus, a value of K0 = 92 GPa is obtained for ScFe2H3.2.

Keywords: Laves phases; hydride; high pressure; intermetallic compounds

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-40455

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Team

Head

NameBld./Office+49 351 260Email
Prof. Dr. Kristina KvashninaROBL/21.6.04+33 476 88 2367

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 Bright+33 476 88 2462
Dr. Damien PrieurROBL/21.6.03+33 476 88 2463
Dr. André Roßberg801/P3162758
Anne Thielena.thielenAthzdr.de