The surface properties of a van der Waals fluid

Surface properties are obtained from an extension of the direct simulation Monte Carlo algorithm to a hard sphere system with an infinite range, weak attractive potential that obeys the van der Waals equation of state. Liquid–vapor surface tension measurements both with and without a gravitational field are in agreement with models summarizing experimental values for simple substances. These measurements are also in agreement with the van der Waals predictions using the measured interface density profile provided the square gradient term identification with a divergent free energy expansion is ignored. The divergent term should be replaced by one that takes into account the work required to form the density gradient in the reference hard sphere system.