密度泛函理论研究Nb2Gen(n=1～4 )团簇
A density functional investigation of Nb2Gen ( n = 1～4) clusters

运用密度泛函方法在(U)B3LYP/ LanL2DZ水平上对Nb2Gen(n=1~4)团簇进行了系统的理论研究，得到Nb2Gen(n=1~4)团簇的最低能结构的几何构型和电子性质.优化结果表明：Nb2Gen(n=1~4)团簇最低能结构的自旋多重度均为单重态.团簇最低能结构的电子态与团簇的大小有关.当n为奇数时，团簇的电子态为1A1，n为偶数时电子态为1A.通过对计算平均束缚能和分裂能发现：Nb2Gen(n=1～4)团簇中热力学稳定性最强的是Nb2Ge2团簇；最弱的是Nb2Ge4团簇．自然电荷分布的结果说明Nb2Gen(n=1～4)团簇中当n=1-2时，电子转移正常，而当n=1-2时出现电荷反转现象.同时还研究了HOMO-LUMO 能隙、磁性和红外光谱.
The geometric structures of the Nb2Gen(n=1~4) clusters are investigated computationally by density functional method at the (U)B3LYP/ LanL2DZ level. The lowest-energy structures are obtained. The results indicate spin configurations of the lowest-energy structure of Nb2Gen(n=1~4) are singlet. The results were found that the electronic states of the Nb2Gen(n=1~4) clusters associated with the odevity of the spin multiplicity, namely the electronic states were 1A1 when n was odd, and the electronic states were 1A when n were even. The calculated atomic averaged binding energies and fragmentation energies manifest that thermodynamic stability of Nb2Ge2 cluster is strongest in the lowest-energy Nb2Gen(n=1~4) clusters. Meanwhile natural populations manifest that the charges transfer mainly from Nb atoms to Si atom in the lowest-energy Nb2Ge and Nb2Ge2 clusters, while Nb2Ge and Nb2Ge2 clusters are in reverse. The HOMO-LUMO gaps, magnetism and Infrared spectra of the lowest-energy Nb2Gen(n=1~4) clusters are investigated as well.