SimGen(m+n=9)团簇结构和电子性质的计算研究

硅锗团簇结构与电子性质的研究对于研发新型微电子材料具有重要意义. 将遗传算法和基于密度泛函理论的紧束缚方法相结合, 研究了Si_mGe_n(m+n=9)团簇的原子堆积结构和电子性质. 计算结果发现, Si_mGe_n(m+n=9) 团簇存在两种低能原子堆积稳定构型: 带小金字塔的五边形双锥堆积和带桥位Ge原子的四面体紧密堆积. 随着团簇内锗原子数目的逐渐增加, 两种堆积结构均出现明显的转变, 其中最低能量的几何结构由单侧带相邻双金字塔的五边形双锥结构转变为双侧带相邻单金字塔的五边形双锥结构. 随着原子堆积结构的变化, 团簇内原子电荷分布及电子最高占据轨道与电子最低未占据轨道的能隙随团簇内所含硅和锗元素组分的不同呈现出明显的差异.

Computational study of structures and electronic properties of SimGen (m+n=9) clusters

The researches of the structural and electronic properties of silicon and germanium clusters are of great significance for developing novel microelectronic materials. This paper aims to study the geometric structures and electronic properties of Si_mGe_n (m+n=9) clusters by combining genetic algorithm and density functional tight binding method. The study shows that there are two low energy stable atomic stacking configurations for Si_mGe_n(m+n = 9) clusters: one is a pentagon double cone stacking two small adjacent pyramids, the other is a tetrahedron close packing with a Ge atom on a bridge. Both stacking configurations are changed greatly with gradually increasing the Ge atom number in the cluster. The shape of the lowest-energy configuration changes from the pentagon double cone stacking two adjacent pyramids on the same side into the pentagon double cone stacking two adjacent pyramids on both sides of the up and down. With this change, the electron distribution and the gap of the highest occupied molecular orbital and the lowest unoccupied molecular orbital gap are obviously dependent on the difference in components of Ge and Si elements contained.