TRANSITION-METAL OXIDE CHEMISTRY - ELECTRONIC-STRUCTURE STUDY OF WO3,REO3, AND NAWO3

In this paper, we present the results of electronic structure, ab init io calculations performed on ReO3, WO3, and the stoichiometric tungste n bronze NaWO3. We examine the relation between the structural and the electronic properties of the three materials and comment on the solid state chemistry governing the interaction between the transition meta l and its oxygen ligands. We show that off-center displacements of the W ion in WO3 are driven by the onset of covalent interactions with th e nearest oxygen, while the metallic materials ReO3 and NaWO3 are stab le when cubic. In the latter case, antibonding contributions due to th e occupation of the conduction band oppose the deformation. The differ ent behavior is justified by examining the band structure of the compo unds. The effect of the different number of valence electrons and of t he different nature of the transition metal on the electronic distribu tion in the solid are analyzed. Finally, by comparing the mechanical p roperties of the three oxides, we show that the antibonding conduction electron makes ReO3 very rigid and can suggest an explanation for the pressure-induced phase transition observed for this material.