Theoretical study of adsorption of propanethiol on Au(111) surface at different coverages

Abstract

By applying the first-principles method based on the density functional theory, we study the non-dissociative adsorption of C3H7SH molecule and the dissociated adsorption of C3H7S group both on Au(111) surface at five kinds of coverages (1/16, 2/16, 3/16, 4/16, 1/3). It is found that both the tilt angle and the adsorption energy are affected by coverage. When the coverage increases to 1/3, the tilt angle of the molecular axis reduces 6°–10°, and the adsorption energy reduces 0.21 eV. At a saturated coverage, the absorption properties are especially studied for three Au(111) surface structures of (3×3), (2√3×2√3 ight)R30° and 2√3×3. For the non-dissociative adsorption of C3H7SH at the saturated coverage, both the adsorption configurations and adsorption energies are almost the same for the three surface structures. But for the dissociated C3H7S group, the adsorption energies of surface structures of (2√3×2√3 ight)R30° and 2√3×3 are about 0.05-0.07 eV higher than that of the (3×3) surface structure. Effects of the van der Waals interaction on the adsorption configuration and energy are investigated by the DFT-D2 method. For the non-dissociative adsorption of C3H7SH/Au(111) system at a saturated coverage of 1/3, the van der Waals interaction reduces the interaction distance between the adsorbate and the substrate, and corrects the adsorption energy by 0.53 eV, which is close to experimental result.