Analysis of Electronic Structure and X-ray Absorption and Emission Spectra in MgO within the FP-LAPW Method

Abstract

In this work we calculated MgO ab initio X-ray Absorption and Emission spectra using the Full Potential Linearized Augmented Plane Wave method within the Density Functional Theory formalism. The X-ray Absorption and Emission spectra for the K and L2;3 edges of Mg and O atoms were calculated including a core hole in order to study the electronic structure of valence and conduction bands of the system. Both kinds of spectra were compared with experimental data obtaining a very good agreement and the improvement in the spectra due to the use of Tran Blaha modified Becke-Johnson (TB-mBJ)potential is manifested. This potential describes better the insulator properties, produces a band gap that is in good agreement with the experimental value and improves the intensities and the structure of the spectra. Was interesting to find the presence of Mg d states below the Fermi energy in the equilibrium volume of MgO. The XANES experiments were better reproduced by introducing the full core hole in the calculations using TB-mBJ potential while for XES the best agreement was obtained without core hole. The Bader’s topological method was employed to analyse the ionic behaviour. Using the electronic charges obtained with the Bader’s Method and the equilibrium lattice parameter, we obtained the value of the Lattice Energy and we compared it with the value obtained by the Born-Haber cycle showing a good agreement. The charge density for MgO was plotted, and a maximally localized Wannier function for O is shown.