Ab Initio Perturbed Ion Calculations on Oxo- and Fluoroperovskites

Abstract

The electronic structure of KMgF3, KZnF3, RbCaF3, and SrTiO3 has been calculated by means of the ab initio Perturbed Ion method at several values of the cell size. The study includes (a) analysis of core and valence energies and their variation with the crystal geometry; (b) obtaining of local ionic densities consistent with the lattice interactions; (c) calculation of crystal properties like lattice energy, equilibrium cell parameter, and bulk modulus, and (d) determination of separate ionic contributions to the chemical bonding. Particular attention is paid to the small but highly significant non-classical energy terms appearing in the formalism, as well as to the effects of the electron correlation in the computed properties. The global results show that the aiPI method gives as good a performance as that found for simpler crystals like alkali halides and MgO.