Why the Water Adsorbed on Metal Surface Tilted—the Quantum Chemical Study of Water Adsorbed on Al(111)and Cu(100)

Ab initio molecular method is used to theoretically investigate the interactions of water with theCu(100)and Al(111)surface.Cu5,Al4 and Al10 clusters are used to simulate the different kinds of surfaces.At different basis set level of H2O in adsorption system,the potential energy surface of the HOH plane tilted of three systems are calculated.Without consideration of the d orbitals of the oxygenatom,the optimized structure is the water plane normal to the surface,and the H2Otilting of40o～50 ois found to require smallamount of energy.When the d orbitals of oxygen atom aetaken into account,the calculated structure of adsorbed H2O monomer with an inclined molecular axis such as Cu50o,Al40o is in an agreement with experimental results.The results indicate that the d orbitals of oxygena tom have the critical effect on the structure of the adsorbed H2O monomer.