Adsorption-induced surface stress on a c(4 × 2) adatom surface by an alkanethiol

Abstract

We investigate the surface stresses induced by an alkanethiol adsorbing onto a Au(1 1 1) surface in a supercell. The surface stresses of the adatom and clean surfaces are determined using density functional theory calculations with the opt-B86b vdW and PBE functionals. We find that the Au(1 1 1) surface with adatoms leads to a reduction in the intrinsic tensile surface stresses, which is in agreement with analytical results from elastic field theory. When methanethiols adsorb onto the clean Au(1 1 1) surface, charge directly redistributes from the surface gold atoms to the methanethiols. On the other hand, when methanethiols adsorb onto the adatom Au(1 1 1) surface, the adatoms shield the effect of charge redistribution from the surface gold atoms to the methanethiols. This shielding mechanism weakens Au–S bonding, and results in lower adsorption-induced compressive surface stresses than for the clean surface.