STRUCTURAL AND CHEMICAL-STABILITY OF HALIDE PEROVSKITES

The ab initio Perturbed Ion (aiPI) quantum mechanical method is used t o study the solid state reaction: AX + MX2 --> AMX(3) from a thermodyn amical point of view. The reaction energy is first determined by means of static calculations (i.e. at null absolute temperature) on the ide al cubic structures of the components. The very difficult problem of d etermining the most stable crystal structure of a compound is then und ertaken by examining the differences in energy among many structures r eported for AX, MX2 and AMX(3) compounds. Finally, the reaction energy is again examined in the light of those corrections, and the results are used to analyze the experimental data available on the synthesis o f perovskites. (C) 1997 Elsevier Science Ltd.