Short range solvation forces in fluids

Abstract

A formalism based on a linearization procedure is used to obtain an expression for the thermodynamic potential of a system of fluid particles in terms of the local particle number density and bulk structure factor. For the case of adsorption of particles at a single impenetrable interface, minimization of the thermodynamic potential yields an integral equation for the number density identical to that obtained by Percus. From the thermodynamic potential for our model we obtain the force/unit area between two plates which is simply related to the surface density of fluids at the plates. The equations are solved numerically for the one-dimensional hard rod fluid and the three-dimensional Percus-Yevick fluid. The resulting density and force show pronounced oscillations in agreement with recent Monte Carlo calculations. The magnitude of the force is comparable to van der Waals interactions and can thus modify significantly forces that exist between colloid particles.