Density functional theory study of the adsorption of methanthiol on Au(1 1 1): Role of gold adatoms

• For the first time the adsorption of CH3SH on Au(1 1 1) with intrinsic defects are studied.
• The effect of surface defect on CH3SH/Au(1 1 1) before and after the S–H cleave is different.
• The presence of Au adatom assists the dissociation of CH3SH on Au(1 1 1).

By performing density functional theory calculations, this work clarifies the sites and energetics of both the non-dissociative and dissociated adsorptions of CH3SH on clean Au(1 1 1) and Au(1 1 1) with intrinsic defects. It was found that the adsorption on defect-free Au(1 1 1) is most stable for non-dissociative CH3SH. Its direct molecular dissociation to form CH3S/Au and H/Au is barred by an activation barrier of 0.9 eV. However, the presence of neighboring Auad can assist the dissociation reaction to form CH3S–Auad–H by lowering the energy barrier to 0.6 eV. As for the dissociated CH3S, the surface geometry of two CH3S joined by a Auad is the most favorable one.