中文摘要：

采用第一性原理方法研究了五种覆盖度下甲硫醇在Au（111）面的吸附构型和吸附能.分别对于S—H解离前CH3SH和S—H解离后CH3S,计算其在不同覆盖度下的吸附结构和能量.结果显示各种覆盖度下CH3SH都优先吸附于top位,倾斜角为70°±2°,在低覆盖度（1/12,1/9,1/8）下的吸附能最大,为0.33～0.35 eV;而CH3S在各种覆盖度下稳定吸附于bri-fcc位,倾斜角为48.3°～58.5°,低覆盖度下的吸附能为2.08 eV.对于CH3SH和CH3S的吸附,吸附能均随覆盖度的增大而减小.重点研究了范德华力对高覆盖度吸附的影响.在覆盖度为1/3时,采用DFT-D2方法,分别计算了CH3SH和CH3S的吸附,结果显示范德华力使吸附物和Au表面的距离减小,同时使CH3SH和CH3S的吸附能分别增大为0.59 eV和2.27 eV.DFT-D2方法修正使CH3SH的结果更接近实验结论,但使CH3S的结果偏离实验值.

英文摘要：

By applying the first-principles method based on density functional theory, we have studied the adsorptions of non-dissociative CHaSH molecule and dissociated CHaS group on Au（11 l） surface at five different coverage （1/12, 1/8, 1/6, 1/4, 1/3）. By performing the total energy calculations for both CH3SH and CH3S at four possible adsorption sites at every studied coverage, we have found the stable non-dissociative adsorption configuration, as well as the dissociated adsorption for CH3SH from low to high coverage. Especially, the effect of van der Waals interaction on the adsorption configurations and energies have been studied by the DFT-D2 method. Our results suggest that the top site is most stable site for non-dissociative CHaSH molecular at all the studied coverage, while the tilt angle of the adsorbed molecule is 70°±2°. The adsorption energy decreases with the increasing of the coverage, that is 0.33-0.35 eV at low coverage region of 1/12- 1/8. On the other hand, the dissociated CH3S group prefers to adsorb on bri-fcc site at all coverage with the tilt angle of 48.3~~ 58.5~. For the dissociated CHaS, the adsorption energy also decreases with the increasing of the coverage, that is 2.07-2.08 eV at low coverage region of 1/12-1/8. At the saturated coverage of 1/3, the effect of van der Waals interaction was inves- tigated for the adsorption of CH3SH/Au（111） and CH3S/Au（111） systems. The calculation results indicate that the van der Waals force makes the adsorbates closer to the substrate and the adsorption energy larger. The respective adsorption energies for CH3SH and CH3S are about 0.59 eV and 2.27 eV at coverage of 1/3. The calculation result by DFT-D2 method for CH3SH agrees with the experimental conclusion, but that for CH3S is away from the experimental observation. Moreover, our calculation results on the electronic structure show us that charge is transferred from the adsorbed CHaSH and CH3S to the Au substrate. And the amount of the transferred charge decrease with the increase of th