The Inverted Temperature Profile Across a Vapor/Liquid Surface Analyzed by Molecular Computer Simulations

Abstract

We calculate transfer coefficients in a one-component system from molecular simulations of heat and mass transport across a vapor/liquid surface. We present a criterion in terms of these coefficients for an inverted temperature profile to exist across the surface. The profile exists if condensation takes place from an undersaturated vapor, or if evaporation takes place against a supersaturated vapor. This is found to happen if the attractive forces between particles are relatively short range. It does not happen for Lennard–Jones particles, but it may happen for Lennard–Jones spline particles. They more closely resemble hard spheres, in the sense that the second virial coefficient is closer to the value found from the repulsive part of the interaction potential alone, and therefore compare better with results from kinetic theory. A condensation coefficient of unity gives a lack of internal consistency in the data for Lennard–Jones particles. The transfer coefficients for these particles are farther from the ones given by kinetic theory.