Structures of Nanoalloy Clusters AunAln (n=1-10) and the Growth Patterns to the Bulk Phase

Gold nanoclusters have attracted intense interests due to their unique applications as catalysts. The properties of the gold clusters can often be extended through alloying with other metals, by virtue of adding new degrees of freedom and increasing the versatility of bonding. Here, we reported a new series of bimetallic clusters AunAln (n = 110) determined from the density functional calculations. Particle swarm global minimum searches, coupled with density functional optimization, were used to identify low-lying structures of the AunAln clusters and the crystalline phase, in addition to the experimentally known AuAl and Au2Al2 structures. Significantly enhanced binding energies were calculated in stable AunAln clusters compared with their pure Au or Al counterparts as a result of polarized AuAl interactions. The polarization is due to a high electron affinity of gold induced by strong relativistic and shell structure effects. In addition, an Au2Al2 unit was identified as the common motif for lowest-energy structures from Au2Al2 to Au10Al10, and up to the crystalline phase. This information serves to the understanding of new clusters formation and their growth mechanism to the corresponding bulk phase. The present results welcome experimental studies of the predicted clusters which may lead to the discovery of novel properties in this microscopic form of matter, bridging between free atoms and the bulk matter.