Free energy approach to the formation of an icosahedral structure during the freezing of gold nanoclusters

The freezing of metal nanoclusters such as gold, silver, and copper exhibits a structural evolution. The formation of the icosahedral (Ih) structure is dominant despite its energetic metastability. The dynamical aspects of the structural transformations, which are eventually responsible for the kinetics, are studied by calculating free energies of gold nanoclusters. The transition barriers have been determined by using the umbrella sampling technique. Our calculations show that the formation of Ih gold nanoclusters is attributed to the lower free energy barrier from the liquid to the Ih phase compared to the barrier from the liquid to the face-centered-cubic crystal phase.