THEORETICAL-ANALYSIS OF THE ELECTRONIC-STRUCTURE OF PURE AND HYDRATEDFORMS OF AS2O5

A tight-binding method is applied to study the electronic structure of the orthorhombic and tetragonal phases of pure As2O5 as well as its h ydrated crystalline compounds As2O5.5/3H2O and As2O5.4H2O. From the ca lculated density of states we give the contribution of the atomic stat es to the x-ray photoemission valence-band spectrum. As atoms in tetra hedral environments exhibit a characteristic peak which is not found f or As in octahedral coordination. In the case of hydrated oxides we pr edict a smaller valence-band width than in the pure oxides.