Statistical mechanical and quasithermodynamic calculations of surface densities and surface tension

Abstract

The Born-Green-Yvon-Bogolyubov integrodifferential equation for the density in a plane transition zone between liquid and gas in a Lennard-Jones fluid is solved after approximating the pair distribution function by a simple combination of its bulk values. The density profiles so obtained are all monotomic functions in excellent agreement with the profiles obtained from quasithermodynamic models. The surface tension and the stress tensor differences in the interface, calculated from the statistical mechanical model of Kirkwood and Buff are compared with the corresponding quasithermodynamic values and with the experimental values of the surface tension for argon. It is found that the Kirkwood-Buff formula, in the present approach, predicts a much stronger dependence of the surface tension on the curvature of the transition zone than the quasithermodynamic approach.