Calculation of Solid-Fluid Interfacial Free Energy with Consideration of Solid Deformation by Molecular Dynamics Simulations.

ABSTRACT

Fluid-fluid interfacial free energy can be measured accurately and can also be calculated from molecular simulations. However, it is challenging to measure solid-fluid interfacial free energy directly. Accurate computation has not yet been advanced by molecular simulations. In this study, we derive working expressions for estimating solid-fluid interfacial free energy based on the free-energy perturbation method with consideration of solid deformation. A Lennard-Jones solid-fluid system is simulated. Our derivations indicate that the effect of solid deformation is pronounced on solid-fluid interfacial free energy, and the results may be significantly different from the conventional test area method. Our results reveal that the contribution of the solid deformation highly depends on the stress conditions in the solid, which can be either positive or negative. Adsorption of fluids onto the solid surface has a significant effect on interfacial free energy. In weak adsorption, the interfacial free energy is close to the solid-vacuum surface free energy. Strong adsorption results in a significant reduction in interfacial free energy.