Crystal Orbital Overlap Population and X‑ray Absorption Spectroscopy

We present an extension
of an ab initio numerical
tool calculating X-ray absorption spectroscopies and crystal orbital
overlap populations at the same time. Density functional theory is
used to calculate the electronic structure in both occupied (valence
to core X-ray emission spectroscopy) and nonoccupied states (i.e., X-ray absorption near the edge structure and X-ray
magnetic circular dichroism) and to evaluate the orbital overlap typifying
the covalency between neighboring atoms. We show how the different
features in the experimental spectra can be correlated to the chemical
bonds around the absorbing atoms in several examples including acrylonitrile
molecules, rutile TiO2, Li2RuO3 high-energy
density cathode, ZnO, and anti-ferromagnetic V2O3.