甲醇在Au(111)表面吸附的密度泛函研究

 采用基于第一性原理的密度泛函理论和周期平板模型相结合的方法,对CH3OH分子在Au(111)表面top, fcc, hcp和bridge位的吸附模型进行了构型优化、能量计算以及Mulliken布居分析,结果表明top位是较有利的吸附位. 吸附的CH3OH解离产生甲氧基CH3O和H, 对它们在Au(111)面的吸附进行的计算表明, bridge和fcc位分别是二者的最佳吸附位. 对过渡态的计算给出了CH3OH在Au表面解离吸附的可能机理: 首先发生 O-H 键的断裂,继而生成甲氧基中间体.

Density Functional Theory Study of Methanol Adsorption on Au(111) Surface

The first-principles density functional theory (DFT) and self-consistent periodic calculation were used to investigate the methanol adsorption on Au(111) surface. The adsorption energy, equilibrium geometry, and vibrational frequency of CH_3OH on four possible sites (top, hcp, fcc, and bridge) on Au(111) surface were predicted and compared with the experimental data. In the equilibrium adsorption models, the O-H and O-C bonds are elongated, and the stretch vibrational frequency is red shifted. Meanwhile the O-H bond is activated greatly. On all the four sites, the electron transfers from methanol to the metal surface, and the favorite adsorption occurs at the top site. The possible decomposition pathway was investigated with transition state searching by using complete LST/QST methods. The calculation results prove that decomposition of methanol to methoxy and hydrogen occurs on the Au(111) surface, which is in agreement with the available experimental results. The favorite adsorption sites for methoxy and hydrogen are bridge and fcc sites, respectively.