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采用分子模拟方法对硫醇分子在Au(111)表面上的吸附行为进行了研究。对于化学吸附过程,采用了密度泛函理论(DFT)的算法对甲基硫醇和2-巯基乙醇的吸附结构和能量进行了分析。优化结果显示在头基硫原子的多种吸附位置中bridge-fcc位是最稳定的,S-C键相对于金表面法线形成53~54°的倾斜角。对于全覆盖率下的自组装有序结构,采用了分子动力学方法比较了3种不同排布形式的稳定性,结果证明含有3种链取向的C(4×2)结构最稳定。另外,采用DFT方法对电子结构的分析显示,在bridge-fcc吸附位上,硫原子的p电子和邻近的金原子的d电子通过杂化形成了新的成键轨道和反键轨道,这一过程通过对硫和金原子反应前后的局部态密度的分析,进行了详细的论证。
Adsorption behavior of thiol molecules on Au (111) surface was investigated by molecular simulation. For the chemisorption process, the adsorption structure and energy of methyl mercaptan and 2-mercaptoethanol were analyzed using the density functional theory (DFT) algorithm. The optimization results show that the bridge-fcc site is the most stable among the various adsorption sites of the head-on sulfur atom, and the S-C bond forms a tilt angle of 53- 54 ° with respect to the normal to the gold surface. For the self-assembled ordered structure with full coverage, the molecular dynamics method was used to compare the stability of three different arrangements. The results show that the C (4 × 2) structure containing three kinds of chain orientation is the most stable. In addition, the DFT analysis of the electronic structure shows that at the bridge-fcc adsorption site, the p-electrons of the sulfur atom and the d-electrons of the adjacent gold atom form new bonding and antibonding orbital by hybridization The process is demonstrated in detail by analyzing the local state density before and after reaction of sulfur and gold atoms.