Calculation of the interfacial free energy of a fluid at a static wall by Gibbs-Cahn integration.

The interface between a fluid and a static wall is a useful model for a chemically heterogeneous solid-liquid interface. In this work, we outline the calculation of the wall-fluid interfacial free energy (gamma(wf)) for such systems using molecular simulation combined with adsorption equations based on Cahn's extension of the surface thermodynamics of Gibbs. As an example, we integrate such an adsorption equation to obtain gamma(wf) as a function of pressure for a hard-sphere fluid at a hard wall. The results so obtained are shown to be in excellent agreement in both magnitude and precision with previous calculations of this quantity, but are obtained with significantly lower computational effort.