THEORETICAL INVESTIGATION OF HYDROXYLATED OXIDE SURFACES

A self-consistent electronic structure calculation, in the slab geomet ry, is performed to model the dissociative adsorption of water on seve ral oxide surfaces in the limit of complete saturation. We discuss the adsorption characteristics along a series of oxides presenting a grow ing acidity: BaO, SrO, CaO, MgO, TiO2, and SiO2, and on three MgO surf aces: (100), (110), and (211) on which the atoms have different enviro nments. Special emphasis is borne on the charge transfers, the densiti es of states and the oxide gap modification upon hydroxylation. We sho w that these quantities are dependent upon the coverage and that unsta ble MgO surfaces are more reactive towards water dissociation. Finally , by optimizing the geometry on the three MgO surfaces, we discuss the link between the electronic and structural degrees of freedom on hydr oxylated surfaces.