First-principles calculations of oxygen vacancy in CaO crystal

Abstract

We alleviate the band edge problem by adopting the advanced hybrid density functionals (with Alkauskas’s method). The finite-size correction scheme (FNV) is employed to align the defect formation energy. The defect formation energies of oxygen vacancies in CaO crystal with different charge states (0, +1, +2) are researched based on density functional theory. Firstly, we optimize all structures. Afterwards, the structures of defects with three charge states are analyzed. In the end, we give the accurate description of optical spectra for F and F+ centers containing electron-phonon coupling. Based on our computing results, the absorption and luminescence spectra of the F center are peaked at 3.11 eV and 2.60 eV, the luminescence spectrum of the F+ center is peaked at 3.84 eV, and the results are in agreement with the experimental conclusions that the results are 3.10 eV, 2.10 eV and 3.35 eV respectively. We can draw a conclusion that these methods are feasible for the computation of the optical spectra of point defects. Furthermore, their main advantage is that the computational expense and the computing requirements are within our computing power and they are far less than the computing requirements of the many body perturbation theory within the GW (Green’s function is multiplied by screened Coulomb potential) approach. In other words, our methods combine the advantages of various methods in the previous study to solve problems that other methods cannot settle. Thus, we can provide a reference to future’s studies on the point defects by employing these methods.