Some general aspects of solid oxides

Abstract

In the application of solid oxides to actual materials, problems selections modifications, and sometimes molecular engineering are necessary. Some semiquantitative tools are reviewed with attention to broad applicability rather than to a detailed knowledge of special materials. The electrostatic model is very useful for many oxides. If applicable, computer techniques permit the rapid calculation of lattice self-potentials, potentials at interstitial sites and field strengths at ionic sites. Complicated irregular structures are equally assessible as highly symmetric structures. Some recent calculations in V2O5 and MoO3 are quoted as examples. Another tool is the full use of crystallographic data, which are available for many oxides. Small deviations from the real positions of the ions can lead to useful idealizations. The electrostatic energies of the real and the ideal structure give a first order estimate of the usefulness of the idealizations. The concept of kryptomodifications is very helpful in this context, be it more in a qualitative than in a quantitative interpretation. The solid solubility of MoO3 in V2O5 is used as an example.