Multiplet calculations of L_2,3 x-ray absorption near-edge structures for 3d transition-metal compounds

The purpose of this work is to compare the two different procedures to calculate the L_2,3 x-ray absorption spectra of transition-metal compounds: (1) the semi-empirical charge transfer multiplet (CTM) approach and (2) the ab initio configuration-interaction (CI) method based on molecular orbitals. We mainly focused on the difference in the treatment of ligand field effects and the charge transfer effects in the two methods. The reduction of multiplet interactions due to the solid state effects has been found by the ab initio CI approach. We have also found that the mixing between the original and the charge transferred configurations obtained by the ab initio CI approach is smaller than that obtained by the CTM approach, since charge transfer through the covalent bonding between metal and ligand atoms has been included by taking the molecular orbitals as the basis functions.