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.

Comment on “Calculation of Solid–Fluid Interfacial Free Energy with Consideration of Solid Deformation by Molecular Dynamics”

“…γ ★ = γ σ ll 2 /ϵ ll for solid–vacuum and solid–liquid systems. Corresponding open symbols are from Figure 8 in ref . The statistical uncertainties are smaller than the size of the symbols.…”

“…In a recent study, Wu and Firoozabadi (henceforth WF) have sought to identify the role of solid deformations in γ sl defined as where s and l indicate solid and liquid, respectively, A is the interfacial area, and F is the Helmholtz free energy of the solid–liquid system. For fluid phases, the analogous quantity is the interfacial tension; following Gibbs, we refrain from giving this quantity any name for a system with a solid–liquid interface.…”

“…The authors propose their a posteriori correction based on the following differential relation (eq 8 in ref )­ for the system with the solid–fluid interface. Here σ ij are components of the stress tensor and ε ij are the components of the strain tensor.…”

Phase‐Field Simulation of Hydraulic Fracturing by CO2, Water and Nitrogen in 2D and Comparison With Laboratory Data

“…The material's resistance to fracture propagation is characterized by the critical energy release rate G c . In a solid in contact with a fluid, G c is related to solid-fluid interfacial energy density (Wu & Firoozabadi, 2021). The adsorption of a fluid to rock surface affects the interfacial energy density.…”

Reply to “Comment on ‘Calculation of Solid–Fluid Interfacial Free Energy with Consideration of Solid Deformation by Molecular Dynamics Simulations’”

“…We appreciate Parambathu et al.’s interest in our work . As stated in our paper, we derive working expressions for calculating solid–fluid interfacial free energy based on the free-energy perturbation method with consideration of solid deformation .…”