First-principles study of the interaction between molecules and a gold surface

The thiol group can be attached to gold surfaces strongly and thus can be used as a bridge for molecular wires in nanoelectronics. By using density functional theory, we have investigated the interaction between a thiol-phenyl molecule (4-4'-dimereaptodibenzene) and a gold surface with ab initio method. The frontier orbit theory and the perturbation theory are employed to determine constant of the interaction energy quantitatively, which is a parameter in describing the current-voltage properties of molecular wires by the elastic scattering Green function method. The numerical results show that the bonding between the sulfur atom and the gold atoms corresponds mainly to the covalent bond. Some molecular orbits are extended over molecule and gold cluster that certainly give channels for the charge transport, other molecular orbits are localized and the charge transport can take place by tunnel mechanism.