Threshold electronic structure at the oxygen K edge of 3d-transition-metal oxides:: A configuration interaction approach

It has been generally accepted that the threshold structure observed in the oxygen K-edge x-ray absorption spectrum in 3d-transition-metal oxides represents the electronic structure of the 3d transition metal. There is, however, no consensus about the correct description. We present an interpretation which includes both groundstate hybridization and electron correlation. It is based on a configuration-interaction cluster calculation using an MO6 cluster. The oxygen K-edge spectrum is calculated by annihilating a ligand hole in the ground state, and is compared to calculations representing inverse photoemission experiments in which a 3d transition-metal electron is added. Clear differences are observed related to the amount of ligand holes coated in the ground state. Two "rules" connected to this are discussed. A comparison with experimental data of some early transition-metal compounds is made, and shows that this simple cluster approach explains the experimental features quite well. [S0163-1829(99)03028-3].