Computer simulation of fluids interacting with fluctuating walls

Abstract

We present a new method for performing molecular simulations of systems with planar interfaces in the presence of fluctuating walls. The technique is essentially the realization of a frictionless piston exerting an external potential on a fluid within a container. The simulation cell is constructed by placing walls at each of the two ends and allowing periodic boundary conditions in the other two directions. Instead of holding the walls rigid, as in a conventional NVT simulation, an external field is imposed on either one or both walls which are free to move. In this paper we focus on a dynamic implementation of the method. The simplest case is a constant external force which is equivalent to imposing a constant normal pressure. We test the method through comparisons with conventional NVT molecular dynamics simulations. The results of these calculations indicate that the new method is both practical and reliable.