Molecular Dynamics Simulations of Competitive Freezing in Gold Nanoclusters

Molecular dynamics simulations are used to study the competitive freezing of icosahedral, decahedral, polydecahedral, and face-centered cubic structures in gold nanoclusters for a range of cluster sizes and temperatures. Measuring the probability of observing each cluster type in an ensemble of freezing events, along with the overall rate at which liquid drops freeze to any structure, allows us to calculate the rate of formation for each structure. An analysis of the freezing trajectories of the clusters reveals that both the icosahedron and the decahedron structures nucleate through the initial formation of a 5-fold symmetric cap. The icosahedron then continues to grow through the sequential growth of neighboring tetrahedral subunits, while the decahedral cluster grows out from the cap along the central 5-fold axis of symmetry.