The Be K-edge in beryllium oxide and chalcogenides : soft x-ray absorption spectra from first-principles theory and experiment

We have carried out a theoretical and experimental investigation of the beryllium K-edge soft x-ray absorption fine structure of beryllium compounds in the oxygen group, considering BeO, BeS, BeSe, and BeTe. Theoretical spectra are obtained ab initio, through many-body perturbation theory, by solving the Bethe–Salpeter equation (BSE), and by supercell calculations using the core-hole approximation. All calculations are performed with the full-potential linearized augmented plane-wave method. It is found that the two different theoretical approaches produce a similar fine structure, in good agreement with the experimental data. Using the BSE results, we interpret the spectra, distinguishing between bound core-excitons and higher energy excitations.Funding Agencies|Linkoping Linnaeus Initiative for Novel Functional Materials (LiLi-NFM)||Swedish Research Council (VR)||VR grant|691-2011-4426|Swedish National Infrastructure for Computing (SNIC)||Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan||European Theoretical Spectroscopy Facility (ETSF)||Deutsche Forschungsgemeinschaft|SFB 410|