A CLUSTER STUDY OF RB ATOM CHEMISORPTION ON A GAAS(110) SURFACE

Different possible adsorption sites of rubidium atoms on a GaAs(110) s urface have been investigated using ab-initio self-consistent Hartree- Fock energy cluster calculations followed by detailed correlation inve stigations at the level of fourth-order many-body perturbation theory. The Hay-Wadt effective core potentials have been used to represent th e cores of the rubidium, gallium and arsenic atoms. We find that the R b atom adsorption at a site modelled with a RbGa5As4H12 cluster is mos t favoured energetically followed by Rb adsorption at a site modelled with a RbGa4As5H12 cluster. Significant charge transfer from the Rb at om to the GaAs surface is also found to occur, with Ga atoms losing ch arge and As atoms gaining charge. Finally, comparisons are made among different alkali atom adsorptions on the GaAs(110) surface.