Ab Initio Perturbed Ion Calculations on Oxo- and Fluoroperovskites

Abstract

The electronic structure of KMgF_3, KZnF_3, RbCaF_3, andSrTiO_3 has been calculated by means ofthe ab initio Perturbed Ionmethod at several values of the cell size. The study includes (a)analysis of core and valence energies and their variation with thecrystal geometry; (b) obtaining of local ionic densities consistentwith the lattice interactions; (c) calculation of crystal propertieslike lattice energy, equilibrium cell parameter, and bulk modulus,and (d) determination of separated ionic contributions to thechemical bonding. Particular attention is paid to the small buthighly significant non-classical energy terms appearing in theformalism, as well as to the effects of the electron correlationin the computed properties. The global results show that the aiPImethod gives as good a performance as that found for simpler crystalslike alkali halides and MgO.