Structural and electronic properties of AuIr nanoalloys

The lowest-energy structures of binary (AuIr) n , (AuIr 3 ) s , and (Au 3 Ir) s clusters, with n = 2−20, and s = 5, modeled by the many-body Gupta potential, were obtained by using a genetic-symbiotic algorithm. These structures were further relaxed within the density functional theory to obtain the most stable structures for each composition. Segregation is observed in all the AuIr clusters, where the Ir atoms occupy the cluster core and the Au atoms are situated on the cluster surface. On the other hand, there is experimental evidence that the (AuIr) n nanoalloys could have an enhanced catalytic activity for CO oxidation. In order to study this phenomenon, we also performed first-principles density functional calculations of the CO and O 2 adsorption on these bimetallic nanoclusters, considering three different compositions and a fixed cluster size of 20 atoms.