不同覆盖度下丙硫醇在Au(111)面吸附的理论研究

采用基于密度泛函理论的第一性原理方法研究了丙烷硫醇 (C₃H₇SH)在Au(111)面五种覆盖度(1/16, 2/16, 3/16, 4/16, 1/3) 下的未解离和解离吸附的结构、能量和吸附性质. 发现丙烷硫醇的倾斜角和吸附能均受覆盖度影响, 计算结果显示丙烷硫醇的倾斜角随着覆盖度的增大减小了6°–10°, 吸附能随覆盖度的增大减小了0.21 eV. 特别针对饱和覆盖度, 研究了三种可能的表面结构: (2√3×2√3 ight)R30°, 2√3×3和(3×3). 发现S–H键未解离时三种表面结构的吸附构型和吸附能基本一致; S–H键解离后, (2√3×2√3 ight)R30°和2√3×3结构的吸附能比以(3×3)结构的吸附能约高0.05–0.07 eV, 说明C₃H₇S在Au(111)面吸附时, 倾向于形成(2√3×2√3 ight)R30°和2√3×3结构. 此外, 采用DFT-D2方法对饱和覆盖度下C₃H₇SH分子在Au(111)面的吸附进行了范德华修正, 结果显示分子间相互作用使吸附物和Au表面的距离减小, 该相互作用对吸附能的修正值为0.53 eV, 修正后结果与实验结果接近.关键词：第一性原理覆盖度表面结构范德华力

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 ight)R30° and 2√3×3. For the non-dissociative adsorption of C₃H₇SH at the saturated coverage, both the adsorption configurations and adsorption energies are almost the same for the three surface structures. But for the dissociated C₃H₇S group, the adsorption energies of surface structures of (2√3×2√3 ight)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.
Keywords：first principlecoveragesurface structurevan der Waals