Electronic structure of Eu2+-doped SrAl2O4 using modified Becke-Johnson exchange potential

The optimized electronic structure of Eu2+-doped SrAl2O4 is calculated by using the modified Becke-Johnson potential combined with the local density approximation. The calculated minimum energy gap of SrAl2O4 is 6.9 eV, which is close to the experimental value (~6.5 eV). When a Eu atom replaces one of the Sr atoms, Eu 4f majority-spin states appear in the forbidden gap of SrAl2O4, which is estimated to be 5.5 eV above the valence band maximum. Considering spin-orbit coupling, Eu 4f majority-spin states decompose into two energy states and Eu 4f minority-spin states also appear in the band gap of SrAl2O4.