Parametrization of perovskite structures: an ab initio study

An overview of the pressure, temperature and chemical composition dependenc e of the lattice distortion in orthorhombic ABO perovskite structures is pr esented. Within the framework of the so-called global parametrization metho d (GPM) [Thomas (1998). Acta Cryst. B54, 585-599] an improved description f or the position of the A cation in terms of the AO(12) and BO6 polyhedral v olume ratio is proposed. The relationship is derived from an extensive ab i nitio study based on the density functional theory. The applicability of th e improved GPM in combination with ab initio total energy calculations in t he prediction of changes in the structural distortion under increasing hydr ostatic pressure is investigated. Test calculations are performed for the g eophysically important magnesium silicate perovskite and the results are co mpared with the available theoretical and experimental data.