A model for the solid–liquid interfacial free energy at high pressures

For the ubiquitous process of solidification, the solid–liquid interfacial free energy is necessary for modeling the phase-transition kinetics using classical nucleation theory (CNT)-based methods, since it dictates the height of the nucleation energy barrier. However, interfacial free-energy models in prior literature tend to make restrictive approximations (such as being at or near the melt temperature and/or at ambient pressures), which may break down in dynamic-compression experiments where metastable liquids are deeply undercooled or overpressurized before solidifying. We derive a solid–liquid interfacial free-energy model for such high-pressure conditions that is applicable to both metallic and nonmetallic systems and allows an examination of the structure and thickness of the interface. We apply our interfacial free energy model to CNT-based kinetics simulations of dynamic-compression experiments that involve the liquid water–ice VII phase transition and find good agreement with only minor empirical fitting.