Structural, mixing, electronic and magnetic properties of small Cu-Pd nanoalloy clusters

Abstract

Bimetallic CumPdn nanoalloy clusters of small size (m+n ≤ 12) are systematically studied using the spin polarized density functional theory to understand the evolution of structural, mixing, electronic and magnetic properties with size and composition of the binary system. The lowest-energy configurations of the series of bimetallic clusters are determined from unbiased global search with genetic algorithm. With the increase of size, Cu-Pd clusters tend to adopt compact geometries. For a given cluster size, Pd atom prefers the outer position, while Cu atom favors the inner site. Stability analysis reveals that nanoalloy formation for CumPdn clusters is favored for the overall range of sizes and compositions. The small changes in structures of magic clusters with their neighboring compositions indicate that their high stability is primarily due to the variation in composition, not to the change in structure. The electronic state of the Pd atom is promoted upon the formation of the Cu-Pd nanoalloy clusters, while that of the Cu atom remains almost unchanged. The magnetic moments of CumPdn clusters exhibit an evident oscillation behavior with the composition, which can be attributed to the substantial hybridization between the electronic states of Pd and Cu.