物理化学学报 >> 2013, Vol. 29 >> Issue (02): 263-270.doi: 10.3866/PKU.WHXB201211231

理论与计算化学 上一篇    下一篇

甲硫醇在Cu(111)表面的解离吸附: 密度泛函理论研究

范晓丽, 刘燕, 杜秀娟, 刘崇, 张超   

  1. 西北工业大学材料学院, 凝固国家重点实验室, 西安 710072
  • 收稿日期:2012-08-13 修回日期:2012-11-19 发布日期:2013-01-14
  • 通讯作者: 刘燕 E-mail:liuyan2011723@163.com
  • 基金资助:

    国家自然科学基金(20903075, 21273172),高等学校学科创新引智计划(111) (B08040)及西北工业大学基础研究基金(JC20100226)资助项目

Dissociative Adsorption of Methanethiol on Cu(111) Surface: a Density Functional Theory Study

FAN Xiao-Li, LIU Yan, DU Xiu-Juan, LIU Chong, ZHANG Chao   

  1. State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, P. R. China
  • Received:2012-08-13 Revised:2012-11-19 Published:2013-01-14
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20903075, 21273172), Programof Introducing Talents of Discipline to Universities, China (111 Project) (B08040), and Northwestern Polytechnical University Foundation for Fundamental Research, China (JC20100226).

摘要:

采用基于密度泛函理论的第一性原理方法和平板模型研究了CH3SH分子在Cu(111)表面的吸附反应.系统地计算了S原子在不同位置以不同方式吸附的一系列构型, 第一次得到未解离的CH3SH分子在Cu(111)表面顶位上的稳定吸附构型,该构型吸附属于弱的化学吸附, 吸附能为0.39 eV. 计算同时发现在热力学上解离结构比未解离结构更加稳定. 解离的CH3S吸附在桥位和中空位之间, 吸附能为0.75-0.77 eV. 计算分析了未解离吸附到解离吸附的两条反应路径, 最小能量路径的能垒为0.57 eV. 计算结果还表明S―H键断裂后的H原子并不是以H2分子的形式从表面解吸附而是以与表面成键的形式存在. 通过比较S原子在独立的CH3SH分子和吸附状态下的局域态密度, 发现S―H键断裂后S原子和表面的键合强于未断裂时S原子和表面的键合.

关键词: 甲硫醇分子, Cu(111)表面, 密度泛函理论, 吸附构型, 解离, 局域态密度

Abstract:

The interaction of methanethiol (CH3SH) molecules with the Cu(111) surface was investigated using a first-principles method based on density functional theory, and a slab model. A series of possible adsorption configurations constructed using S atoms on different sites with different tilt angles were studied. It was found for the first time that the non-dissociative molecular adsorption of CH3SH on the Cu(111) surface with the S atom sitting on the top site belongs to the weak chemisorption, and the adsorption energy is 0.39 eV. After the dissociation of the S―H bond, the S atom is located at the bridge site, with a small shift toward the hollow site. The dissociative adsorption structure is thermodynamically more stable than the intact one, and the adsorption energy is 0.75-0.77 eV. Two reaction pathways have been studied for the transition from non-dissociative adsorption to dissociative adsorption, and the activation energy barrier along the minimum energy path is 0.57 eV. The results of the calculations indicated that the released H atom prefers to form a bond with the copper surface, rather than desorbing in the H2 molecular form. Comparing the local density of states of S atoms in the single CH3SH, CH3SH/Cu(111), and CH3S/Cu(111) structures, we found that the bonding between the S atoms and the substrate is much stronger in the dissociated adsorption states.

Key words: Methanethiol molecule, Cu(111) surface, Density functional theory, Adsorption geometry, Dissociation, Local density of states

MSC2000: 

  • O641