First-principles identification of charge-transition levels of native defects in BaF2

This paper reports on semilocal and hybrid density functional analysis of charge transition levels of native defects in BaF2 structure. The transition level is defined as the Fermi level where two defect charge states have the same formation energy. The errors arising from the small supercell size effects have been relieved through extrapolating the formation energies to the limit of infinite supercell size. The level placement in the corrected band gap is achieved using a correction factor obtained from the difference between the valence band maxima in semilocal and hybrid calculations. The band gap size from hybrid calculation is validated using the full-potential, linearized augmented planewave method with the modified Becke Johnson exchange potential. Our results are sufficiently accurate and, thus, significant for direct comparison with experiments.