Analysis of pre-edge of oxygen K-edge X-ray absorption spectra of transition metal oxides

The recently developed MBXAS[1] formalism is a powerful tool for inexpensive, accurate simulation of X-ray absorption spectroscopy (XAS). By approximating the final (initial) many-body state as a Slater determinant of all electronic orbitals obtained in presence (absence) of the core hole, one can accurately simulate the electronic relaxation resulting from core-excitation, while maintaining computational advantage by staying within a mean-field framework, such as density functional theory (DFT). In collaboration with experimentalists, we used MBXAS to simulate the oxygen-K edge XAS of 3-d transition metal oxides (TMO). The onset-energy of each spectrum is determined from total energy differences of ground and excited state DFT calculations. For a given transition-metal, the first O K-edge pre-peak energy decreases with increasing valence, indicating strong contribution of metal 3-d levels in the conduction band edge via hybridization. Unlike transition-metal L-edge spectra, which are dominated by local atomic ligand field effects, the O K-edge essentially maps the conduction bands. The oxygen-K edge offers us an opportunity to plot the first-peak positions of all TMOs with a common energy scale.
[1] PhysRevB.97.205127