物理化学学报 >> 1992, Vol. 8 >> Issue (03): 376-382.doi: 10.3866/PKU.WHXB19920317

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铝原子簇上化学吸附的尺度效应及其理论模型

李林峰; 顾宪章; 曹轩; 廖沐真; 吴国是   

  1. 清华大学化学系，北京 100084
  • 收稿日期:1991-03-20 修回日期:1991-09-09 发布日期:1992-06-15
  • 通讯作者: 吴国是

Size-Dependence of Chemisorption on Aluminum Clusters and its Theoretical Model

Li Lin-Feng; Gu Xian-Zhang; Cao Xuan; Liao Mu-Zhen; Wu Guo-Shi   

  1. Department of Chemistry, Tsinghua University, Beijing 100084
  • Received:1991-03-20 Revised:1991-09-09 Published:1992-06-15
  • Contact: Wu Guo-Shi

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摘要： 对铝原子簇Al_n(n=1～10,12,13)已报导过的理论预测几何构型进行合理选择, 用量子化学CNDO/2法研究了单分子一氧化碳在这些簇上取不同吸附位形时的吸附作用。结果表明吸附强度随簇尺度的变化呈“幻数”特性: Al_2、Al_6、Al_(12)簇具有特别高的吸附能, 与实验观测结果相符。采用作者建议的推广电子壳模型可合理解释这一尺度效应。对Al_(12)和Al_(13)簇电子结构的分析进一步支持了壳模型的观点。随着簇的增大, 尺度效应逐步减弱并趋向于体相铝的性质。

关键词: 微原子簇, 铝原子簇, 吸附, 电子壳模型, 一氧化碳

Abstract: Theoretical investigations have been made on the monomolecular adsorption of carbon monoxide on aluminum clusters Al_n(n=1-10, 12, 13). The equilibrium adsorption positions and the binding energies of various CO sites have been evaluated by using the quantum chemical method of CNDO/2 with properly choosing the optimal geometries of aluminum clusters from the reported data. The results reveal that the adsorption of CO on Al_n remarkably depends upon the number of metal atoms in the cluster and exhibits a notable "magic number" behavior, viz. the adsorption energies on Al_2, Al_6 and Al_(12) appear in particularly large values, which are in encouraging agreement with the experimental observations and that predicted by our Extended Electron-Shell Model proposed previously. The analysis of the electronic structure of Al_(12) and Al_(13) puts the model on a still solid basis. It can also be seen that such a size-dependence goes down with the increasing cluster size and the behavior of cluster gradually approaches to that of bulk aluminum.

Key words: Microcluster, Aluminum cluster, Adsorption, Electron-Shell Model, Carbon monoxide