content_image/349268.jpg
<img src='content_image/349268.jpg'>

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 $^{9}$. 

## C. The HSCH$_{2}$COO − molecule on the surface 

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 

