Many-body and anisotropy effects in x-ray absorption spectra of pristine and defective vanadium pentoxide

X-ray absorption spectra of vanadium pentoxide (${\mathrm{V}}₂{\mathrm{O}}₅$) at the vanadium $K$ and $L$ edges are studied with multiple scattering calculations and good agreement with experiment is obtained when the full-potential and multichannel extensions of multiple scattering theory are used. The spectral shapes are analyzed in terms of the local electronic structure at the vanadium sites and they reveal strong anisotropy and final-state correlation effects. The strong polarization dependence of the spectra is explained by the low-symmetry ligand field and vanadyl bonding. The effect of oxygen vacancies, the major intrinsic defect type of ${\mathrm{V}}₂{\mathrm{O}}₅$, is investigated. Clear spectral changes are found for vanadium atoms next to an oxygen vacancy, which may serve as a fingerprint of defects in electron energy loss spectroscopy.