Structures and Chemical Ordering of Small Cu−Ag Clusters

The structures and chemical ordering (segregation properties) of Cu−Ag clusters with 34, 38, and 98 atoms have been studied using a combination of a genetic algorithm (GA) global optimization technique coupled with the Gupta semiempirical many-body potential. A detailed analysis of Cu−Ag structural motifs and segregation effects is presented. For the 38-atom cluster, the effect of varying the potential parameters is studied, where the heteronuclear Cu−Ag parameters in the Gupta potential are derived as weighted averages of the Cu−Cu and Ag−Ag parameters. The structural motifs predicted by the Gupta potential, for selected compositions, have been compared to previously published Gupta and density functional theory (DFT) calculations for 38-atom Cu−Ag clusters. From this study, we have found that the lowest energy arrangement is the CucoreAgshell configuration. For the 98-atom clusters, it was seen that Leary tetrahedron isomers are higher in energy than the isomers obtained by the GA.