The goal of this work is to provide a detailed description of the freezing mechanism in gold clusters. This is accomplished by using constrained Monte Carlo simulations combined with parallel tempering algorithms to evaluate the free energy barriers for various temperatures with respect to crystalline order parameters on a 456 atom cluster. <p>Our simulation results help us to challenge the usual assumption of classic nucleation theory where nucleation starts at the center of a cluster, showing instead that nucleation is favored by freezing started at the surface. We study simplistic phenomenological models for surface freezing and find that the three phase contact line free energy term must be included in order to properly describe the features of the free energy barriers. <p>Furthermore, we propose an alternative free energy parameter with which we are able to identify a kinetic spinodal temperature where the nucleation barrier disappears and find that the critical cluster size remains finite at the limit of stability of the fluid phase. This result is supported by Molecular Dynamics simulations.

The goal of this work is to provide a detailed description of the freezing mechanism in gold clusters. This is accomplished by using constrained Monte Carlo simulations combined with parallel tempering algorithms to evaluate the free energy barriers for various temperatures with respect to crystalline order parameters on a 456 atom cluster. <p>Our simulation results help us to challenge the usual assumption of classic nucleation theory where nucleation starts at the center of a cluster, showing instead that nucleation is favored by freezing started at the surface. We study simplistic phenomenological models for surface freezing and find that the three phase contact line free energy term must be included in order to properly describe the features of the free energy barriers. <p>Furthermore, we propose an alternative free energy parameter with which we are able to identify a kinetic spinodal temperature where the nucleation barrier disappears and find that the critical cluster size remains finite at the limit of stability of the fluid phase. This result is supported by Molecular Dynamics simulations.