L2,3 X-RAY-ABSORPTION EDGES OF D0 COMPOUNDS - K+, CA-2+, SC-3+ AND TI-4+ IN OH (OCTAHEDRAL) SYMMETRY

The L2,3 x-ray-absorption edges of 3d0 compounds are calculated with use of an atomic description of the 2p63d0 to 2p53d1 excitation, with the inclusion of the crystal field. For reasons of clarity, we confine ourselves to d0 compounds in octahedral symmetry, but the same approach is applicable to all other dN compounds in any point-group symmetry. The experimental spectra of FeTiO3, Sc2O3, ScF3, CaF2, and the potassium halides are well reproduced by the present calculations, including the previously misinterpreted small leading peaks. The splitting between the two main peaks in both the L3 and L2 edge are related, though not equal, to the crystal-field splitting. Comparison to experiment showed that the broadening of the main multiplet lines is different. This can be related to Coster-Kronig Auger processes for the L2 edge and to a solid-state broadening which is a combination of vibrational (phononic) and dispersional broadenings. With the full treatment of the atomic multiplets, the atomic effects can be separated from solid-state effects, which offers a better description of the latter. This includes vibrational broadenings, the covalent screening of the intra-atomic Coulomb and exchange interactions, via the position of small leading peaks, and surface effects. The same general framework can be used to discuss crystal-field effects in both lower symmetries, with the possibility of polarization-dependent spectra (e.g., TiO2), and partly filled d bands. © 1990 The American Physical Society.