Computer simulation of the gas/liquid surface

The gas/liquid surface of a system of 255 Lennard-Jones (12,6) molecules has been simulated by Monte Carlo sequences at three reduced temperatures which span most of the liquid range. The results at the two higher temperatures show a monotonic profile of density as a function of height, but those at a temperature close to the triple point suggest that the liquid just below the surface can form layers; that is, that local density is an oscillatory function of height. This phenomenon is compared with similar previous results and it is concluded that it may well be the consequence of the constraints applied to the simulated system rather than an inherent property of a free liquid surface.Preliminary densities for a mixture have also been calculated.