晶面上化学吸附的量子化学计算新方法

在金属单晶表面的化学吸附和催化行为的研究,对较有说服力地建立催化剂活性中心模型和建立催化机理具有重要意义。而在金属单晶表面上的化学吸附和催化转化的量子化学计算,则是这种与“真实”催化体系平行研究的一个组成部分。表面量子化学的理论处理,大体有两种近似模型,即从固体能带理论出发的半无限晶体模型与从分子轨道理论出发的

A NEW METHOD OF QUANTUMOCHEMICAL CALCULATION FOR CHEMIISORPTION ON CRYSTAL SURFACE PLANE

In this article, surface atom are classified into two types: A-type and B-type atom, and it is prooposed that the atoms constructing directly cluster active-site on surface are designated as A- type atoms and the atoms of the near neighbor (or, the next neighbor may also be included, if neccessary) to Type-A atoms are designated as B-type atoms. Such contemplation to show and to distinguish various micro-environments of coordination of Type-A atoms. Type-A atoms form chemisorption bond(s) directly with chemisorbed gas molccule (s), and Type-B atoms, through interal chemical boundings with Type-A atoms in the bulk of crystal, make Type-A atoms tied to a certain extent, so as to weaken their chemical activity. Thus the difference in the surface free valency of Type-A atoms and in their coordination micro-environments among surface planes with different crystal orientation can be demonstrated. This method possesses some merit common to cluster model and semi-infinite thinfilm model the localized interaction of chemisorptive system can intuitivelly be trcoted as in cluster model, and on the other band, the general properties of crystal surface plances can also be considered as in thinfilm model.