Orbital breathing effects in the computation of x-ray d-ion spectra in solids by ab initio wave-function-based methods

TL;DR

This paper introduces an ab initio computational method that explicitly includes relaxation and polarization effects in calculating x-ray spectra of transition-metal ions in solids, improving accuracy over previous phenomenological models.

Contribution

The paper develops a new ab initio scheme that accounts for orbital breathing effects in x-ray spectra calculations, enabling more precise modeling of complex correlated oxides.

Findings

Good agreement with experimental data for Li₂CuO₂

Determined absolute scattering intensities for transition-metal L-edges

Methodology applicable to complex $d^n$ electronic structures

Abstract

In existing theoretical approaches to core-level excitations of transition-metal ions in solids relaxation and polarization effects due to the inner core hole are often ignored or described phenomenologically. Here we set up an ab initio computational scheme that explicitly accounts for such physics in the calculation of x-ray absorption and resonant inelastic x-ray scattering spectra. Good agreement is found with experimental transition-metal $L$-edge data for the strongly correlated $d^9$ cuprate Li$_2$CuO$_2$, for which we determine the absolute scattering intensities. The newly developed methodology opens the way for the investigation of even more complex $d^n$ electronic structures of group VI B to VIII B correlated oxide compounds.