A density functional study on the adsorption of methanethiolate on the (111) surfaces of noble metals

The adsorption energies and structures of methanethiolate, SCH3, on the (11 1) surfaces of Au, Ag, and Cu have been studied using a density functional theory. The results obtained for the Au surface are in good agreement with experiments and previous calculations. The strength of the adsorption energ ies is found to be Cu > Ag > Au, and the nature of the chemisorption bond i s discussed. The strong interaction between the SCH3 and Cu surface can be explained in a similar way to that as for the binding energy of SCH3 with m etal atoms. Scalar-relativistic effects in the adsorption energies and adso rption structures, which dominate the differences observed between the Ag a nd Au surfaces, are studied using quasirelativistic and nonrelativistic pse udopotentials. The relativistic effects decrease the adsorption energy of S CH3 on the Au(111) surface, although the binding energy of the AuSCH3 compl ex is increased by relativity. The unexpected relativistic effects are also discussed. (C) 2001 American Institute of Physics.