摘要
对α Al2 O3( 0 0 0 1)晶体表层三种不同终止原子结构的计算模型 ,在三维周期边界条件下的κ空间中 ,采用超软赝势平面波函数描述多电子体系 .应用基于密度泛函理论的局域密度近似 ,计算了不同表层结构的体系能量 ,表明最表层终止原子为单层Al的表面结构最稳定 .对由 10个原子组成的菱形原胞进行了结构优化 ,得到晶胞参数值(a0 =0 4 8178nm)与实验报道值误差小于 1 3% .进一步计算了超晶胞 ( 2× 2 )表面弛豫 ,弛豫后原第 2层O原子层成为最表层 ;对不同表层O ,Al原子最外层电子进行了布居分析 ,表面电子有更大的概率被定域在O原子的周围 。
There are three different structures of the α Al 2O 3(0001) crystal surface because different atoms are terminated on the outermost layer. Our calculations are based on the density functional theory in local density approximation, and on ultra soft pseudopotential methods, with the valence orbital expanded in plane wave by using three\|dimensional periodic boundary conditions in κ space, firstly, the calculation result is that α Al 2O 3(0001) crystal surface structure which the outermost layer is terminated by a single layer of Al atoms is much more stable than the other two structures. Secondly, a rhombohedral primitive cell is employed to perform cell optimizations, with ten atoms in the unit cell, and the calculated equilibrium parameters are: a 0=0 48178nm,γ=120 16, which are in excellent agreement with recent experimental values( a 0=0 47591nm),with a difference of less than 1 3%. Moreover, our calculations are performed with a super cell slab model in vacuum environment, in which the outermost layer is terminated by single Al atoms. By investigating the four\|layer relaxation and Al O atoms population of the surface, we obtain results that the top single Al layer is an inward relaxation of 0 0792 nm—0 098nm, that is, the second\|layer O atoms are turned into the top layer,and the top O and Al atoms population analysis show that the valence electrons are concentrated on the surface oxygen ions with a greater probability,it is obvious that the α Al 2O 3(0001) crystal surface appears in the O\|surface state,which is discussed from the microstructure of α Al 2O 3(0001)crystals in details.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2003年第9期2268-2273,共6页
Acta Physica Sinica
基金
四川省应用基础研究项目 (批准号:0 2GY0 2 9-0 0 6)
四川省教育厅重点项目 (批准号:2 0 0 2A0 86)资助的课题~~
