A test of a two-density theory of surface tension

Abstract

The mean-field approximation for the gas–liquid surface of the penetrable sphere model is shown to be a good approximation by comparison with a Monte Carlo simulation. It is used as a standard by which to judge the improvement effected in a van der Waals theory of surface tension by going from a “one-density” to a “two-density” representation of the local free energy. This change is shown to yield a more accurate expression for the number density as a function of height and a lower and hence more accurate value of the surface tension.