A density functional theory study of the adsorption of sulfur, mercapto, and methylthiolate on Au(111)

We have studied the adsorption of sulfur (S=), mercapto (HS–), and methylthiolate (CH3S–) on Au(111). The three adsorbates are found to form strong bonds to the gold surface through the S-end. While the sulfur atom adsorbs in the high coordinated fcc site, the mercapto and methylthiolate molecules adsorb in bridge or bridgelike sites. The bending of the sulfur–hydrogen and sulfur–methyl bonds away from the surface normal plays a key role in this sites preference. We show that the back bonded sulfur species prefer the bridge sites because of lower steric repulsion at these sites between the gold surface and the hydrogen and methyl groups, respectively.