Dynamik II: Bewegungsprobleme

Abstract

A hybrid Hartree-Fock and d. functional theory, in which Hartree-Fock exchange is mixed with d. functional theory exchange functionals, using Beckes' three-parameter method, combined with the non-local correlation functionals by Perdew and Wang, allows us to achieve the best agreement with expt. (11.00 eV) for the BaF2 band gap (11.30 eV). The characterization of F centers in BaF2 is still a question of debate. In order to understand the behavior of the material, we performed ab initio calcns. to det. their electronic structure, at. geometry and formation energy. We also calcd. the M center, the simplest aggregation of two F centers, and the results show that the b band absorption in BaF2 is predominantly due to the presence of M centers.