The Quantum Chemical Study of Water Molecule Adsorbed on Al(111)Surface

Ab initio molecular orbital method is used to theoretically investigate the interactions of water with the different sites of Al(111)surface.Al10 cluster is used to simulate the srface,the adsorption energies and geometries are calculated at different basis site level.The results show that water prefers to adsorb on the top site of the Al(111)surface and it has two stable orientations.When water molecule is farther from the surface,it is adsorbed with hydrogen atom near the surface,then reaches the optimum adsorption site when oxygen atom is near the surface.Giving no consideration of the d orbitals of oxygen atom,the optimum structure is the water plane normal to the surface.When the d orbitals are taken into account,the calculated structure of adsorbed monomer with an inclined molecular axis about 40o is in agreement with the experimental results,so the critical effect of dorbitals of the oxygen atom on the structure of adsorbed water monomer is recognized.Also the effect of charge on the adsorption system is discussed.The results indicate that on the surface with positive charges,oxygen atom is near the surface,Al-O equilibrium distance decreases;on the surface with the negative charge,the results are opposite,H near the surface is the stable structure.