UCL Discovery

Abstract

We present the results of ab-initio Hartree-Fock calculations on a set of perovskite-structured transition metal oxides, in which the transition metal ion has electronic configuration d((0)) . The analysis of the solution, based on a Tight Binding-like examination of the calculated band structures in reciprocal space, allows us to understand the trends in the properties of perovskites as a function of their chemical composition; a parameter is defined which is easily calculated from the band structure of the cubic phase, that quantifies the extent of covalence in the M-O interaction. Ferroelectric-like distortions from the cubic phase are seeded by symmetry breaking around either a M or an O ion of the structure; the electronic perturbation is then transferred to the neighbouring sites via a delocalisation of the pi M-O bonding levels in the valence band.