Long-ranged solvation forces in a fluid with short-ranged interactions

Abstract

The grand canonical Monte Carlo technique is used to calculate the solvation force and interfacial tension in a simple Lennard-Jones fluid confined between two solid walls. Emphasis is placed on large wall-to-wall separations, where the oscillations of density and solvation force due to layering effects have decayed. Despite the short range of the fluid–fluid and fluid–wall interaction potentials used, the solvation force shows an unsuspectedly long-ranged behavior, remaining quite perceptible up to a separation of 100 molecular diameters. It is also found that the sign of the solvation force at large separations is not uniquely determined by the sign of the interfacial tension: The walls that are “philic” with respect to the constrained fluid may well exhibit both repulsive and attractive solvation forces.