Ab initio many-body study of the electronic and optical properties of MgAl2O4 spinel

Abstract

The electronic structure and optical properties of MgAl2O4 spinel with and without oxygen vacancies have been studied in the framework of many-body perturbation theory. By considering the self-energy of electrons, we reasonably describe the bandgap of perfect MgAl2O4 and the defect energy levels of MgAl2O4 containing oxygen vacancies. With the inclusion of electron-hole interaction by solving Bethe-Salpeter equation, the calculated dielectric functions and reflectivity spectrum all are in agreement well with the experimental results for perfect MgAl2O4. Our results show that the sharp peak near 7.8 eV in the experimental absorption spectrum is attributed to the excitonic states. The oxygen vacancies produce some new defect energy levels in the forbidden gap. The optical absorption peaks at 5.3 eV, 4.75 eV and 3.2 eV are induced by the VO0 and VO1+ vacancies.