Theoretical description of optical and x-ray absorption spectra of MgO including many-body effects

Here we report the optical and x-ray absorption spectra of wide-band-gap oxide MgO using density functional theory many-body perturbation (MBPT). Our comprehensive study electronic structure shows that while band gap is underestimated with exchange-correlation PBEsol (4.58 eV) hybrid HSE06 (6.58 compared to experimental value (7.7 eV), it significantly improved (7.52 even overcompensated (8.53 when quasiparticle corrections are considered. Inclusion excitonic effects by solving Bethe-Salpeter equation (BSE) yields spectrum in excellent agreement experiment. Excellent observed also for O Mg K-edge spectra, demonstrating importance electron-hole interaction within MBPT. Projection coupling coefficients from BSE eigenvectors on allows us determine origin prominent peaks identify orbital character relevant contributions. The real-space projection lowest energy exciton wave function indicates a Wannier-Mott type, whereas first K edge more localized.