Theoretical study of the adsorption of water molecule on (TiO 2 ) n ( n =3—6) clusters

Possible adsorption structures of H 2 O on (TiO 2 ) n ( n =3—6) clusters were studied by using genetic algorithm combined with empirical potential function. The structures were further optimized using DFT method B3LYP/6-31G ** . The results show that H 2 O molecule is adsorbed on TiO 2 clusters through the attachment of oxygen atom to the titanium atom with lower coordination number. Molecular orbitals show that the bond between water and cluster is formed mainly by the 3s3p orbitals of titanium，the orbitals of H 2 O keep the basic features unchanged but are more delocalized after adsorption. Combined with population analysis and calculation of vibration frequencies，the results show that the O—H bond becomes weaker after H 2 O is adsorbed on TiO 2 clusters.