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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.
The first-principle method was used to study the adsorption configuration and adsorption energy of methanethiol on the Au (111) surface under the five coverage conditions. For CH3SH and S-H after dissociation of S-H, The results showed that CH3SH preferentially adsorbed on the top with various degrees of coverage, with a tilt angle of 70 ° ± 2 ° and low coverage (1 / 12,1 / 9,1 / 8), the adsorption energy of CH3S was 0.33 ~ 0.35 eV, while that of CH3S was stable at 48.1 ° ~ 58.5 ° at various coverage, and the adsorption energy was 2.08 eV under low coverage. For the adsorption of CH3SH and CH3S, the adsorption energy decreases with the increase of coverage, and the influence of van der Waals forces on the adsorption of high coverage is mainly studied.When the coverage is 1/3, DFT-D2 method is used to calculate The adsorption of CH3SH and CH3S showed that van der Waals forces decreased the distance between the adsorbate and the Au surface and increased the adsorption energies of CH3SH and CH3S to 0.59 eV and 2.27 eV respectively. Close to the experimental conclusion, but the results of the CH3S deviation from the experimental value.