First-principles study of LiBaF sub(3) crystals containing interstitial fluoride

The positions of the interstitial fluoride atoms in LiBaF sub(3) crystal are simulated by GULP. It is found that the formation energy is low when interstitial fluoride atoms at the center of the edge of the cube formed by Ba ions. The electronic structures and absorption bands for the perfect LiBaF sub(3) crystal and the LiBaF sub(3) crystal containing interstitial fluoride have been calculated using density functional theory code CASTEP. It is predicted that the interstitial fluoride atom combine with a formal lattice fluoride ion forming H center causes the 320 nm absorption band.