First-principles study of the electronic structure and optical properties of the pure BaY2F8

Ab-initio calculations based on density-functional theory have been employed to study the electronic structure and some optical properties of the pure BaY2F8 (BYF) crystal. The band gap is calculated to be 7.5 eV. The electronic structure calculations revealed that the top of the valence band is dominated by the fluoride p-states, while the very bottom of the conduction band has predominantly yttrium d-character. The optical response in ultra-violet region is determined by calculating the complex dielectric tensor. It was found that the BYF crystal does not exhibit large optical anisotropy. Its principal absorption occurs due to electronic transitions from populated 2p states of the F to empty d-states of neighboring Y and Ba atoms.