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

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)R30° and 2√3×3. For the non-dissociative adsorption of C₃H₇SH at the saturated coverage, both the adsorption configurations and adsorption energies are al-most the same for the three surface structures. But for the dissociated C₃H₇S group, the adsorption energies of surface structures of (2√3×2√3)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.