gnX(X=Au, Cu; n=1-8)团簇和纯银团簇的结构稳定性和电子性质的比较研究

Using the meta-generalized gradient approximation (meta-GGA) exchange correlation TPSS functional, the geometric structures, relative stabilities and electronic properties of bimetallic AgnX (X=Au, Cu; n=1-8) clusters are systematically investigated and compare them with those of pure silver clusters. The optimized structures show that the transition point from preferentially planar to three-dimensional structure occurs at n=6 for the AgnAu clusters, while n=5 for AgnCu clusters. For different-sized AgnX clusters, one X (X=Au or Cu) atom substituted Agn+1 structures is a dominant growth pattern. The calculated fragmentation energies, second-order differences in energies, and the highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps show interesting odd-even oscillation behaviors, indicating that Ag2, 4, 6, 8 and Ag1, 3, 5, 7X (X=Au, Cu) clusters keep higher stability in comparison with their neighboring clusters. The natural population analysis reveals that the charges transfer from the Agn host to the impurity atom except for Ag2Cu cluster. Moreover, vertical ionization potential (VIP), vertical electronic affinity (VEA) and chemical hardness (η) are in depth discussed and compared. The same odd-even oscillations are found for the VIP and of the AgnX (X=Au, Cu; n=1-8) clusters.