(OsB)_n(n=1-6)团簇结构与稳定性的第一性原理研究

基于第一性原理,采用密度泛函理论(DFT)中的广义梯度近似(GGA)对(OsB)_n(n=1-6)团簇各种可能的构型进行了几何结构优化,得出了各团簇的最稳定构型,并对最稳定构型的能量、结合能、二阶能量差分、能隙等性质进行了理论研究。研究结果表明:n=2、3时,体系的基态结构分别为棱形和锅盖形;n=4时,体系的基态结构是对称性为T_d的立方体形状,是本文对称性最高的构型;从n=4开始立方体构型主导着团簇基态结构的生长行为,表明团簇的稳定性不仅与团簇的尺寸大小有关,还与团簇的对称性有关。团簇(OsB)_4的能隙、结合能与能量的二阶差分比邻近的值都大,说明团簇(OsB)_4有较高的稳定性,n=4是团簇的幻数。

First-principles study of structures and stable properties of(OsB)_n(n=1-6)clusters

Based on first-principles,all the possible geometrical structures of(OsB)_n(n=1-6)clusters are optimized with generalized gradient approximation(GGA)of density functional theory.For the most stable structures,the energy,binding energy,second-order energy difference,energy gap are studied.The calculated results showed the following tendencies:n=2,3,the ground state structures of the system are rhombus and lid-like form,respectively;n=4,the ground state structure is a cubic structure with T_d symmetry,which is the most tiptop for symmetry in the(OsB)_n(n=1-6)clusters;n≥4,the cube configuration dominates the growth behavior of the ground state structures of the clusters,which indicates that the stability of cluster is connected with not only the size of the cluster,but also the symmetry of the cluster.The energy gap,binding energy and second-order energy difference of the(OsB)_4 cluster are larger than adjacent clusters,so the(OsB)_4 cluster has higher stability,and n=4 is the magic number of the clusters.