Global optimization of 8-10 atom palladium-iridium nanoalloys at the DFT level

The global optimization of PdnIr(N-n) N = 8-10 clusters has been performed using the Birmingham Cluster Genetic Algorithm (BCGA). Structures were evaluated directly using density functional theory (DFT), which has allowed the identification of Ir and Ir-rich PdIr cubic global minima, displaying a strong tendency to segregate. The ability of the searches to find the putative global minimum has been assessed using a homotop search method, which shows a high degree of success. The role of spin in the system has been considered through a series of spin-restricted reoptimizations of BCGA-DFT minima. The preferred spin of the clusters is found to vary widely with composition, showing no overall trend in lowest-energy multiplicities.