Cu 表面性质的第一性原理分析

采用第一性原理赝势平面波方法, 计算并详细分析了面心立方Cu晶体及其 (100), (110) 和 (111) 这3个低指数表面的原子结构、 表面能量及表面电子态密度. 表面能的计算结果表明, Cu (111) 表面的结构稳定性最好, Cu (100) 表面次之, Cu (110)表面的结构稳定性最差. 3个表面的表面原子弛豫量随着层数的增加而逐渐减弱. Cu (110) 表面的最表层原子相对收缩最大, Cu (100)表面次之, Cu (111) 表面的最表层原子相对收缩最小. 表面原子弛豫不仅引起表面几何结构的变化, 而且使表面层原子的电子态密度峰形相对晶体内部发生变化, 这是表面能产生的主要原因, 而Cu (110)表面相对于Cu (100)与Cu (111)表面具有高表面活性的主要原因则源于其表面层原子电子态密度在高能级处的波峰相对晶体内部显著的升高. 关键词： Cu 晶体 表面结构 表面能 态密度

First-principles analysis of properties of Cu surfaces

Using first-principles pseudopotential plane wave method, the energy, atomic geometry and electronic density of states of FCC Cu crystal and its (111), (110) and (100) surface models were calculated and analyzed. According to the calculated results of the surface energy, the structural stability of the Cu surfaces increases for Cu (110), Cu (100), Cu (111) surfaces successively. The relaxation extent of the surface atoms decreases successively with the increasing the number of the layers. For the inwards relaxation of the surface layer atoms, Cu (110) surface moves maximum, Cu (100) takes second place, Cu (111) surface moves least. 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 the change of peak contour of density of states (DOS) of surface layer atoms comparing with crystal inside. The increment of the total energy caused by these change is the main reason of the surface energy. And that the Cu (110) surface having higher activity than that of Cu(111) and Cu(100) surfaces may be attributed to its apparent rising of the surface layer atoms DOS in the high energy level.