近些年, 由于硅半导体材料在微电子工业中的潜在应用, 其理论和实验研究备受人们广泛关注。 尤其是过渡金属掺杂的硅团簇材料在物理化学性质方面表现了极好的稳定性。 这些主要归因于过渡金属含有未填满的d轨道电子, 可以填充硅团簇表面的空轨道, 减少团簇表面的悬挂键, 进而提高整个掺杂硅团簇的结构稳定性, 同时产生各种特殊光学、 磁性和超导等性质。 采用密度泛函理论DFT-B3LYP方法对HmTiSin (m=1～2; n=2～8)团簇的几何结构和电子性质进行了理论计算, 讨论了Ti掺杂硅团簇TiSin(n=2～8)及其氢化团簇基态结构的变化规律、 解离通道和HOMO-LUMO能隙等特征。 结果表明, 随着Si原子数目的增加, 在TiSin(n=2～8)团簇中其掺杂Ti原子依次吸附在团簇的棱、 面及结构内部。 当在掺杂团簇表面吸附氢原子时, 都优于吸附在团簇的硅原子上, 而且绝大多数的氢化结构采纳了TiSin团簇的骨架构型。 解离能和HOMO-LUMO能隙的分析结果表明在团簇表面吸附两个H原子时能够明显提高整个团簇的结构稳定性。 二阶能量差分的研究发现TiSi2和TiSi6团簇相对其他团簇具有较高的稳定性, 同时两个H1TiSi7和H2TiSi7氢化团簇的稳定性更高。 此外, 模拟了这些氢化团簇的红外振动特征峰, 对主要特征峰进行了归属。 这些研究将为过渡金属掺杂硅基团簇材料的实验制备和表征提供重要的理论参考。

In recent years, the silicon semiconductor clusters have experimentally and theoretically attracted great attention because of their potential applications regarded as cluster-assembled optoelectronic materials. Especially, the appropriate transition-metal atoms can stabilize the silicon clusters by doping to the surface of clusters, accordingly novel physical and chemical properties of transition-metal doped silicon clusters will be produced, e. g., optical property, magnetic property, and superconductor, etc. In this work, the geometric structures and electronic properties of HmTiSin (m=1～2; n=2～8) clusters are systematically studied using the density functional theory (DFT) B3LYP method, and the changing regularity, dissociation channels and HOMO-LUMO gaps of the ground-state structures of the TiSin(n=2～8) clusters and their hydrides are discussed in detail. The results show that the Ti atom in the TiSin(n=2～8) clusters will gradually move from convex to surface and to interior sites along with the increasing number of the Si atom. For most of hydrogenated HmTiSin clusters, their stable structures keep the structural framework of TiSin clusters, while the H atoms prefer energetically to be attached on the silicon atoms, rather than the Ti atom. The analysis of dissociation energies as well as HOMO-LUMO gaps show that the adsorption of two H atoms on clusters’ surfaces will eliminate the number of dangling bonds in these clusters, and largely improve the structural stability of clusters. The second-order energy differences (Δ2E) can explore the chemical stability of the magic clusters, and it is found that the Δ2E is very sensitive to the cluster size, and has the local oscillation behaviors along with the increasing cluster size, in which the TiSi2 and TiSi6 clusters possess relatively higher stabilities than their neighboring ones, whereas the hydrogenated H1TiSi7 and H2TiSi7 clusters are the most stable in all of clusters studied here. In addition, we simulate the infrared spectra of these hydrogenated clusters, and assign the main vibrational peaks for further experimental references. These studies will provide significant theoretical references for further experimental synthesis and measurements of the transition metal-doped silicon-based nanomaterials.