The electronic structures of fluorides with Frenkel defects were investigated in the tight-binding approximation by using the LMTO method. Defect formation and migration energies were calculated, and the electronic structure and optical excitation of a H center in a defective fluorite structure were examined. It was shown, on the basis of calculations of the binding energies, that CaF2, BaF2 and SrF2 were ionic compounds, but that the chemical bond in PbF2 was partially covalent. Possible methods of displacement of interstitial F atoms, that led to the observed optical spectra of an H center, were investigated.

First-Principles Calculations of the Electronic Structure of Fluorite-Type Crystals (CaF2, BaF2, SrF2 and PbF2) Containing Frenkel Defects - Analysis of Optical and Transport Properties. V.P.Zhukov, V.M.Zaĭnullina: Physics of the Solid State, 1998, 40[11], 1827-32