Ab-initio calculations of the gold-sulfur interaction for alkanethiol monolayers

We have performed ab-initio geometry optimization of SCH3 absorbed on cluster models of Au(111), to examine the gold-sulfur-carbon head group energetics for self-assembled monolayers of alkanethiols on gold. The ab-initio calculations are performed using gradient-corrected density functional theory. The data obtained from these calculations, are used to construct a realistic empirical potential function to describe the complete headgroup-Au(111) energy surface. In particular, the dependence of the energy of the system on theAu surface-sulfur separation, and the surface-sulfur-carbon angle is determined for positions representative of the entire gold(111) surface plane.