Approach combining the Rietveld method and pairs distribution function analysis to study crystalline materials under high-pressure and/or temperature

Abstract

An approach combining the Rietveld method and pairs distribution function analysis was developed and can help to understand the effect of temperature and/or high-pressure on crystalline materials. It was applied to orthorhombic Ta2O5 compound, and the obtained results were compared with the experimental pairs distribution function reported in the literature, and an excellent agreement was reached. The approach permitted to simulate average pairs distribution functions GTa-Ta(R), GTa-O(R), and GO-O(R) and the average radial distribution functions RDFTa-Ta(R), RDFTa-O(R), and RDFO-O(R). The coordination numbers for the first neighbors were obtained, and used in the expression to calculate the Cowley-Warren chemical short-range order parameter {\alpha}CW . The calculated value suggests a preference for forming homopolar pairs in the first coordination shell. Previous study on the effect of high-pressure on orthorhombic Ta2O5 showed a pressure-induced amorphization process. This amorphization can be associated with the preference for forming homopolar pairs in the first coordination shell.