Optical and energy-loss spectra of MgO, ZnO, and CdO from<i>ab initio</i>many-body calculations

We compute optical properties including excitonic effects for the equilibrium polymorphs of three group-II metal monoxides by solving the Bethe-Salpeter equation. The underlying electronic structures are based on results of a recently developed $GW$ approach starting from a hybrid exchange-correlation functional. The resulting quasiparticle band structures are discussed with respect to their mapping on computationally less expensive electronic structures computed using a $\text{GGA}+U$ method together with a scissor operator $\ensuremath{\Delta}$. The efficiency of the latter approach allows the computation of real and imaginary parts of the dielectric function including excitonic effects up to photon energies of 32.5 eV with high accuracy. In addition, we derive the reflectivity as an optical key quantity as well as the energy-loss function. For dominant peak structures we identify the valence bands that mainly contribute to the corresponding transitions. Furthermore, the influence of excitonic effects and the comparison with results from other calculations and measurements are discussed in detail. Chemical trends across the oxides are identified.