Metastable $\beta$ ice holds small guest molecules in stable gas hydrates, so its solid-liquid equilibrium is of interest. However, aqueous crystal-liquid transitions are very difficult to simulate. A new molecular dynamics algorithm generates trajectories in a generalized $NPT$ ensemble and equilibrates states of coexisting phases with a selectable enthalpy. With replicas spanning the range between $\beta$ ice and liquid water, we find the statistical temperature from the enthalpy histograms and characterize the transition by the entropy, introducing a general computational procedure for first-order transitions.

• Received 9 October 2014

DOI:https://doi.org/10.1103/PhysRevLett.114.170601