Ab-initio CI calculations for 3d transition metal L2,3 X-ray absorption spectra of TiCl4 and VOCl3

X-ray-absorption near-edge structures (XANES) at the transition metal (TM) L-2,L-3 edge of TiCl4 and VOCl3 are calculated by the all-electron configuration interaction (CI) method using fully-relativistic molecular spinors with density functional theory (DFT). The electronic excitation from molecular spinors mainly composed of ligand p atomic spinors to those of TM-3d spinors, i.e., the charge transfer, is included by taking additional electronic configurations in the CI. The effects of the ligand field and the charge transfer on the TM-L-2,L-3 XANES are investigated by an ab-intio method. The reduction of inter-electron interaction due to the covalent bonding between TM and ligand atoms has been found. The contribution of charge transferred configuration is small at the initial state of TM-L-2,L-3 XANES while the significant amount of charge transferred configuration is found at the final states. The spectral shapes of TM-L-2,L-3 XANES of both TiCl4 and VOCl3 are strongly modified by the charge transfer effects.