First-principles calculations of oxygen-vacancy dipoles and hydrogen impurities in SrF2

Abstract

The electronic and atomic properties of oxygen-vacancy dipoles and hydrogen impurities, which are important types of point impurities in the alkaline-earth fluoride SrF2, are calculated. The band gap of SrF2 for four different arrangements of O-V dipoles is found at 11.3 eV when calculated with the hybrid B3PW (which is Becke's exchange functionals using Becke's three-parameter method combined with the nonlocal correlation functional of Perdew and Wang) method and is essentially the same as in the perfect SrF2 crystal. On the basis of the calculated density of states the nature of the defect bands in the band structure can be well understood. In addition two kinds of hydrogen impurities (H-s(-),H-i(0)) are also calculated with the B3PW method. We present the corresponding electronic structure and calculate the hyperfine constants at the H-i(0) impurity, which exhibits an unpaired electron, and at its nearest-neighbor fluorine atoms. Our results agree well with the experimental data.