Surface structure and surface tension: Perturbation theory and Monte Carlo calculation

A Monte Carlo computation of the surface structure and surface tension of a liquid with molecules interacting according to the Lennard-Jones 12-6 potential is described. The computation demonstrates the presence of a well-developed layer structure at the surface extending to a depth of about eight molecular layers. The calculated surface tension agrees well with that predicted by Toxvaerd's extension of the Barker-Henderson perturbation theory to nonuniform fluids. The latter theory also predicts well the averaged behavior of the surface density profile (though not the development of the layered structure). This theory is used with accurate pair and triplet potentials to calculate values of the surface tension of liquid argon that agree quantitatively with experiment over a wide range of temperatures.