AB-INITIO STUDIES OF H2O ADSORPTION ON THE TIO2(110) RUTILE SURFACE

The geometrical, electronic and energetic properties of the dissociati ve (1 x 2) adsorption of H2O on the rutile TiO4(110) surface are calcu lated by applying the full potential linearized plane wave method with in the local density approximation. Two possible (1 x 2) adsorption ge ometries are investigated. We find a general reduction of the bond len gths at the surface and an inwards relaxation of the surface plane. Wh ereas the O-H bond lengths are very similar for both geometries and co mparable to that of the free H2O molecule, the corresponding Ti-O bond lengths differ by 0.25 Angstrom, expressing the amphoteric character of the OH groups. Concerning their ground-state energies, both adsorpt ion geometries are practically equal. Additional OH surface peaks appe ar in the density of states, lowered by about -2 eV from the main part s of the O s and p bands of the clean surface. Upon adsorption, the lo west Ti d-like states of the conduction band of the clean surface beco me occupied. Compared with the clean surface, the work function is str ongly reduced by about 3 eV. (C)1998 Elsevier Science B.V. All rights reserved.