Thermal stability of structure in small gold clusters

Abstract

Limits of thermal stability of the original fcc phase in gold clusters up to 3.5 nm in diameter have been studied. The simulation carried out by the molecular-dynamics method using a modified TB-SMA tight-binding potential has shown that in small Au clusters under the effect of the temperature factor there occurs a transition from the original fcc phase to other structural modifications, including those with a pentagonal symmetry. As the size of gold nanoparticles increases, the polytypic-transition temperature shifts toward the melting temperature of the cluster. The results obtained are compared with the data for copper and nickel nanoparticles with similar sizes. It has been shown that, in the case of nickel and copper clusters, it is the transition from the fcc phase into structures with a pentagonal symmetry, which are not found in the bulk state, that is the governing factor; the gold clusters demonstrate a much more intricate behavior.