摘要
采用第一原理赝势平面波方法,计算了Fcc-Ag晶体及其Ag(111)、Ag(110)与Ag(100)自由表面的能量、几何与电子结构。根据表面能的计算,预测了Ag表面的结构稳定性,结果表明密排Ag(111)面结构稳定性最好,低指数奇异面Ag(100)面次之,Ag(110)面的结构稳定性最差。通过对不同表面几何与电子结构的比较,初步分析了其结构稳定性差异的产生原因。表面原子驰豫不仅引起表面几何结构的变化,而且使表面层的电子结构与键合特性发生改变。驰豫后表面层原子的部分价电子跑到了表面层以上的真空区,使表面层原子的电子态密度峰形发生变化,还新形成了表面态,这是表面能产生的主要原因,而Ag(110)表面相对于Ag(111)与Ag(110)表面具有高表面活性的主要原因则源于其表面层原子显著的结构驰豫。
Using first-principle pseudopotential plane wave method, the energetics, atomic geometries and electronic structures of fcc-Ag crystal and its （111）, （110） and （100） surface models were calculated. According to the calculation of surface energy, the structural stability of Ag surfaces, which increases in the following order： Ag（110） 〈 Ag（100） 〈 Ag（111）, was predicted. And the reason that causes the difference of the structural stability was analyzed in terms of comparison their atomic geometries and electronic structures. It was found that the relaxation of the surface atom layers not only causes the change of geometrical structures of the surface models but also leads to variation of their electronic structures and bonding characters. The relaxation makes a part of valence electrons of the surface layer atoms run into the outer vacuum region above surface layers, which results in the change of peak contour of density of states （DOS） of surface layer atoms and the emergence of some new surface states. The increments of the total energy caused by these change are the main reason of their surface energies. And that the Ag（110） surface having higher activity than that of Ag（111） and Ag（110） surfaces may be attributed to its apparent relaxation of the surface layer atoms.
出处
《贵金属》
CAS
CSCD
2006年第2期5-13,共9页
Precious Metals
基金
国家重点基础研究发展规划(TG2000067105)
教育部科技重点项目(104139)
关键词
金属材料
Fcc—Ag
第一原理赝势平面波方法
表面能
电子结构
Metal materials
Fcc-Ag
First principles pseudopotential plane-wave method
Surface energy
Electron configuration
