Nucleation Kinetics using Generalized Ensemble Simulations

The recently developed generalized replica exchange method (gREM) is employed to sample various coexistence phases efficiently, especially the crystal cluster coexisting with its liquid phase. Namely, the gREM method facilitates comprehensive sampling of phase-transition regions by transforming metastable or unstable energy states in the canonical ensemble to stable ones in the generalized ensemble. Using weighted histogram analysis method (WHAM) analysis, the Gibbs energy as a function of temperature curves can be constructed for the liquid, crystal and various coexisting states. Thus, the nucleation barrier can be extracted without using the classification scheme of liquid and crystal particles. Using the classical nucleation theory, applications to the nucleation kinetics of mW water model and NaCl melt demonstrate that the nucleation rate obtained from our simulation method agrees well with the direct measured nucleation rate from simulations with the same model.