CHEMICAL SHIFTS OF X-RAY EMISSION SPECTRA AND EFFECTIVE STATES OF YTTERBIUM IN FLUORIDES: EMBEDDED CLUSTER MODELING OF YbF2 AND YbF3 CRYSTALS

Abstract

Abstract. The YbF2 and YbF3 crystals were studied within the embedded cluster model. The small core relativistic pseudopotentials for the central Yb atom (42 valence electrons) and embedding potentials for Yb and F atoms were constructed. Chemical shifts of Kα1 and Kα2 lines of X-ray emission spectra (XES) were calculated using non-variation one-center restoration technique and relativistic density functional theory (relDFT) with the hybrid exchangecorrelation functional PBE0. It was done in the YbF9Yb12F24 cluster simulating the YbF3 crystal with respect to YbF8Yb12F24 one representing the YbF2 crystal. The resulting estimates are 628 meV for Kα1 and 559 meV for Kα2 and their weighted mean agrees within 10% with the experimental value, 557±27 meV. In turn, the weighted relativistic Hartree−Fock (relHF) calculation is higher on 20%. It indicates that the incorporation of electron correlation effects is essential for reproducing the Kα1, 2 chemical shifts.

Compound-tunable embedding potential method and its application to fersmite crystal

“…In particular, the chemshifts of K α -lines of d/f −elements are mainly sensitive to occupation numbers of appropriate d and f -shells, whereas the chemshifts of K β -lines are already sensitive to distances to the ligands and their types. It is not less important that characteristic XES lines can be easily identified for any atom of interest and the XES chemshifts can be measured on the atoms having sufficient fraction in a material, thus providing data to characterize an effective state of any atom for all these compounds [1,4,5,24,28].…”