On the morse potential in liquid phase and at liquid-vapor interface

Abstract

Canonical Molecular Dynamics simulations have been performed to calculate thermodynamic properties in the liquid phase and at the liquid-vapor interface for fluids interacting by Morse potential. Transport properties such as self diffusion and shear viscosity have been calculated in one phase. Self diffusion shows an important dependence on particle number whereas shear viscosity does not show such dependence. At the liquid-vapor interface, properties such as orthobaric densities, vapor pressure, and surface tension were calculated. Equilibrium densities were compared with results obtained by NpT plus test particle method, and an excellent agreement was found. The surface tension and the vapor pressure are computed for the first time in this work. We also analyzed the cut-off distance dependence in both bulk and interfacial properties. No significant difference was found in the data obtained when two different cut-off distances were used, $R_c=2.5\sigma$ and $R_c=4.0\sigma$. This is a consequence of the short-range nature of the potential.