Measuring solid-liquid interfacial properties outside of equilibrium via synthetic driving force molecular dynamics simulations

Abstract

The solid-liquid interfacial free energy γ and mobility M are critical parameters governing solidification microstructures, but their precise determination outside of equilibrium remains a significant challenge. In this study, we propose a novel computational methodology to determine the temperature-dependent solid-liquid interfacial properties using the Energy-Conserving Orientational (ECO) force within the framework of molecular dynamics (MD) simulations. By introducing a synthetic driving force that opposes the combined effects of curvature and undercooling, we established a system of equations that allows for the simultaneous extraction of interfacial stiffness and mobility. This method is validated using an EAM potential for Nickel across a temperature range from 0.88 to 0.97 of the melting temperature T m . Our results reveal a non-monotonic temperature dependence for the solid-liquid interfacial energy, which initially decreases with increasing temperature before reaching an approximately constant value at higher temperatures. In contrast, the interfacial mobility exhibits an upward trend with increasing temperature; there is some evidence of a structural transformation around 0.92 T m . This work provides a robust and direct atomistic approach to access off-equilibrium interfacial properties without requiring thermodynamic integration or auxiliary simulation techniques and offers new insight into the temperature dependence of interfacial energy.