Surface tension, adsorption and surface entropy of liquid-vapour systems by atomistic simulation

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Abstract
Results of Monte Carlo and molecular-dynamics simulations of Lennard-Jones systems are presented in order to compare various methods of computing interfacial properties of liquid-vapour systems. For the computation of the surface tension gamma a new method is developed, which makes use of the Bennett procedure for calculating free-energy differences. The method is compared with the conventional route to the surface tension via the virial expression. For the temperature derivative of the surface tension, gamma /dT, both a fluctuation equation and the Gibbs adsorption equation are employed. It is found that d gamma /dT is determined more accurately by the absorption equation (through the surface entropy). Results of simulations of binary Lennard-Jones mixtures are also presented. For the argon-krypton system, values of the adsorption of argon at the interface are determined from density profiles, and are compared with values predicted by the adsorption equation. Positive adsorption of argon manifests itself in krypton-rich mixtures as a significant 'bump' in the argon density profile near the interface.

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