Abstract: Using the meta-generalized gradient approximation (meta-GGA) exchange correlation TPSS functional, the geometric structures, the relative stabilities, and the electronic properties of bimetallic Ag_nX (X=Au, Cu; n=1-8) clusters are systematically investigated and compared 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 Ag_nAu clusters, and at n=5 for Ag_nCu clusters. For different-sized Ag_nX clusters, one X (X=Au or Cu) atom substituted Ag_{n + 1} structure is a dominant growth pattern. The calculated fragmentation energies, second-order differences in energies, and the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps show interesting odd-even oscillation behaviours, indicating that Ag_{2, 4, 6, 8} and Ag_{1, 3, 5, 7}X (X=Au, Cu) clusters keep high stabilities in comparison with their neighbouring clusters. The natural population analysis reveals that the charges transfer from the Ag_n host to the impurity atom except for the Ag₂Cu cluster. Moreover, vertical ionization potential (VIP), vertical electronic affinity (VEA), and chemical hardness (η) are discussed and compared in depth. The same odd-even oscillations are found for the VIP and η of the Ag_nX (X=Au, Cu; n=1-8) clusters.

Key words: Ag_nX (X=Au,Cu) clusters, geometric structure, meta-GGA exchange correlation functional