Crystal-Field and Covalency Effects in Uranates

Crystal-Field and Covalency Effects in Uranates: An X-ray Spectroscopic Study

Butorin, Sergei M. (Uppsala University)
Kvashnina, Kristina O. (Helmholtz Zentrum Dresden Rossendorf; European Synchrotron Radiation Facility (ESRF))
Smith, A.L. (TU Delft RST/Reactor Physics and Nuclear Materials)
Popa, Karin (European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe)
Martin, Philippe M. (UMR 5257 CEA/CNRS/UM/ENSCM)

2016

The electronic structure of U^V- and U^VI-containing uranates NaUO₃and Pb₃UO₆was studied by using an advanced technique, namely X-ray absorption spectroscopy (XAS) in high-energy-resolution fluorescence-detection (HERFD) mode. Due to a significant reduction in core–hole lifetime broadening, the crystal-field splittings of the 5f shell were probed directly in HERFD-XAS spectra collected at the U 3d edge, which is not possible by using conventional XAS. In addition, the charge-transfer satellites that result from U 5f–O 2p hybridization were clearly resolved. The crystal-field parameters, 5f occupancy, and degree of covalency of the chemical bonding in these uranates were estimated by using the Anderson impurity model by calculating the U 3d HERFD-XAS, conventional XAS, core-to-core (U 4f–3d transitions) resonant inelastic X-ray scattering (RIXS), and U 4f X-ray photoelectron spectra. The crystal field was found to be strong in these systems and the 5f occupancy was determined to be 1.32 and 0.84 electrons in the ground state for NaUO₃and Pb₃UO₆, respectively, which indicates a significant covalent character for these compounds.

computational chemistry
crystal-field studies
electronic structure
uranium
X-ray absorption spectroscopy

http://resolver.tudelft.nl/uuid:5b6f2d4b-63e0-4540-8a31-ee8674724728

https://doi.org/10.1002/chem.201505091

2017-06-03

0947-6539

Chemistry: A European Journal, 22 (28), 9693-9698

Accepted Author Manuscript

Institutional Repository

journal article

© 2016 Sergei M. Butorin, Kristina O. Kvashnina, A.L. Smith, Karin Popa, Philippe M. Martin