Thermal fluctuations in the interface of an inhomogeneous fluid

Abstract

We use van Kampen's expression for the partition function of a van der Waals gas to investigate the effect of noncritical fluctuations on the interface of an inhomogeneous fluid. Such a procedure combines in a consistent manner the results of mean field theory and of capillary wave theory and, in addition, uncovers contributions due to fluctuations of the interface profile. Although the latter add negligibly to the interfacial width, they result in corrections to the mean field surface tension comparable to those resulting from capillary fluctuations. The effect of the walls in limiting the fluctuations is explicitly taken into account.