Electronic structure, optical properties, and bonding in alkaline-earth halofluoride scintillators: BaClF, BaBrF, and BaIF

Abstract

We report first-principles studies of the structural, electronic, and optical properties of the alkaline-earth halofluorides, Ba$X$F ($X$ $=$ Cl, Br, and I), including pressure dependence of structural properties. The band structures show clear separation of the halogen $p$ derived valence bands into higher binding energy F and lower binding energy $X$ derived manifolds reflecting the very high electronegativity of F relative to the other halogens. Implications of this for bonding and other properties are discussed. We find an anisotropic behavior of the structural parameters especially of BaIF under pressure. The optical properties on the other hand are almost isotropic, in spite of the anisotropic crystal structures.