FIRST-PRINCIPLES INVESTIGATION OF REO3 AND RELATED OXIDES

Electronic-structure calculations are performed, within the local-dens ity approximation to the density-functional theory, using the full-pot ential Linear muffin-tin orbital method to understand the relation bet ween structural and electronic properties of ReO3, WO3, and the stoich iometric tungsten bronze NaWO3. Energy changes associated with small d eformations from the cubic phase indicate that ReO, and the tungsten b ronze an stable when cubic while the W ion in WO3 shows a tendency to off-center displacements. The different behavior is explained by exami ning the band structure of the compounds. Calculated frequencies and e igenvectors of Gamma phonons in ReO3 corroborate the existence of high -frequency modes in this crystal which supports a recent theoretical p roposal for the interpretation of its electrical resistivity.