Pressure dependence of ice nucleation in coarse-grained water models

Molecular dynamics simulations are helpful in revealing the fundamental mechanisms involved in ice nucleation, a topic relevant to understanding ice formation in clouds and efforts to control freezing through enhancing or suppressing ice nucleation. Recent experiments suggest a role for pressure fluctuations in triggering nucleation, yet measurements and simulations of ice nucleation rates at negative pressures are sparse. We evaluate homogeneous ice nucleation rates for the ML-mW and mW water models at pressures ranging from atmospheric pressure to -1000 atm, where we see the nucleation rate increasing monotonically with decreasing pressure. We report that the density difference between water and ice exhibited by these models plays a central role in controlling the nucleation rate at non-atmospheric pressures. From our findings, we confirm that temperature and pressure are interchangeable for achieving a given nucleation rate, and we identify an equation for approximating lines of constant nucleation rate. These results can be useful in making experimental predictions to advance the study of ice nucleation mechanisms.