(MgC)_n(n=1-10)团簇结构稳定性及金属性的第一性原理研究

The structural stability and metallicity of(MgC)_n(n = 1-10) clusters

采用基于密度泛函理论的第一性原理对同比例二元团簇(MgC)_n(n=1-10)的结构稳定性和金属性进行比较系统的研究.结果显示:当原子总数N=2,4,6,8,12时,二元团簇的结构为平面形状,其余为对称性较低的三维构型,且Mg_3C_3为幻数结构.另外,在二元团簇的形成过程中,镁、碳原子并不是均匀分布于空间中,而是首先形成各自倾向的构型,再结合成团簇.同时,(MgC)_n(n=1-10)二元团簇的基态结构在原子总数N=10时发生突变,由平面形向三维结构转变.此外,最高占据轨道和最低未占据轨道间的能隙值除N=8外呈逐渐降低的趋势,说明在同比例二元团簇随尺寸增加的演化中出现半导体性与金属性间的相互转变行为.

The structural stability and metallicity of same proportion binary clusters（ MgC）_n（ n = 1- 10） have been investigated systematically by using the first- principles method based on density functional theory. The results show that the structural shape of binary clusters is plane when the total atom number equals to 2,4,6,8 or12,the others show three dimensional structures,and the Mg_3C_3 is considered as magic structure. Furthermore,the carbon and magnesium atoms are not evenly distributed in space in the process of forming clusters,but incline to form pure carbon and magnesium clusters firstly,and then the binary clusters combine two kinds of clusters. At the same time,the lowest energy configuration transforms form 2D to 3D at N = 10,and the values of HOMO- LUMO energy gaps decrease gradually,except N = 8,it suggests that the same ratio binary clusters present mutual transformation between semiconductor and metallicity.