TABLE II: The geometries and adsorption energies for the structures of the SCH$_{2}$COOH molecule on the Au(111) at 0.25ML. marked configurations are 46.1 ◦ and 41.6 ◦ , respectively. This can be interpreted as when the SCH$_{2}$COOH molecules are deposited on the Au(111) surface, some SCH$_{2}$COOH molecules lie on the substrate (see Fig. 1b), but some of them rise up to a certain level (corresponding to # marked configurations). Thus in the case of SCH$_{2}$COOH, the configurations with different tilted angles may admix, and the molecule appears to deposit on the gold substrate randomly $^{9}$. When the thioglycolic acid is adsorbed on the Au(111) surface, its carboxylic acid group (COOH) can be deprotonated and it becomes HSCH$_{2}$COO − $^{8}$. The optimized adsorption configurations of the HSCH$_{2}$COO − molecule on the Au(111) surface are described in Ta- ble III. The adsorption energies in Table III demonstrate that the sulfur atom in the C. The HSCH$_{2}$COO − molecule on the surface 7 initial θ d$_{S}$$_{−}$$_{Au}$ optimized θ tilt d$_{S}$$_{−}$$_{Au}$ E$_{ads}$ site ˚ A site deg direct ˚ A eV bri 0 2.60 bri-hcp 6.5 fcc 2.48 2.26 #45 2.60 bri-fcc 46.1 hcp 2.45 2.33 90 2.60 bri-fcc 71.3 hcp 2.42 2.17 fcc 0 2.60 fcc 9.8 hcp 2.47 2.28 45 2.60 fcc 51.0 hcp 2.51 2.17 90 2.60 bri-fcc 71.3 hcp 2.50 2.23 hcp 0 2.60 bri-hcp 2.7 fcc 2.47 2.22 #45 2.60 bri-hcp 41.6 fcc 2.46 2.33 90 2.60 bri-hcp 68.0 fcc 2.47 2 . 34 top 0 2.60 top-fcc 10.1 hcp 2.40 2.01 45 2.60 top-fcc 63.0 hcp 2.40 1.89 90 2.60 top-fcc 70.3 hcp 2.59 2.05