A density functional investigation of Nb₂Ge_n (n = 1 ∼ 4) clusters

The geometric structures of the Nb₂Ge_n (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 that spin configurations of the lowest - energy structure of Nb₂Ge_n (n = 1 ∼ 4) are singlet. The results also show that the electronic states of the Nb₂Ge_n (n = 1 ∼ 4) clusters associated with the odevity of the spin multiplicity, namely the electronic states are ¹A₁ when n is odd, and the electronic states are ¹A when n is even. The calculated atomic averaged binding energies and fragmentation energies manifest that thermodynamic stability of Nb₂Ge₂ cluster is strongest in the lowest - energy Nb₂Ge_n (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 Nb₂Ge₃ and Nb₂Ge₄ clusters are in reverse. The HOMO - LUMO gaps, magnetism and Infrared spectra of the lowest - energy Nb₂Ge_n (n = 1 ∼ 4) clusters are investigated as well. (authors)