Electronic Structure of Alkaline-Earth Fluorides Studied by Model Clusters. I. Ground State

Abstract

We present the results of molecular-orbital calculations for alkaline-earth fluorides, i.e., CaF 2 , SrF 2 and BaF 2 . The discrete variational (DV) Xα method is applied to two types of model clusters, i.e., one centered at the cation site and the other at the anion site. Electrostatic potential due to the ions outside the cluster has been calculated with direct summation of the Coulomb potential of point charges by the Coker's method. The electronic structures obtained by the present models agree well with those obtained by photoelectron spectroscopy. The outer-most Ba 2+ 5 p core band is found to have a width of less than 2 eV which is much smaller than the proposed value in interpreting the excitation spectrum of Auger free luminescence and the total photoelectric yield spectrum. The ionic radii of alkaline-earth and fluorine ions in CaF 2 , SrF 2 and BaF 2 are determined by investigating the charge distribution. The ionic radii thus obtained are in good agreement with the crystal values of Shannon and...