Equilibrium vapor pressure and surface tension from cluster data: Density functional results

Abstract

Density functional theory is applied to investigate the possibility of using the data from atomic and molecular clusters for the prediction of equilibrium vapor pressure and surface tension. For this purpose free energies of center of mass clusters constrained to a spherical volume are calculated at various temperatures. Clusters composed of Lennard-Jones atoms and molecules of two Lennard-Jones sites are considered. The desired bulk values are extracted from cluster data using the method by Merikanto and et al. [Phys. Rev. Lett. 98, 145702 (2007)] and a consistent comparison to the exact values obtained from the density functional theory is made. At temperatures not much above the triple point the estimates of both the equilibrium vapor pressure and surface tension are within 4% of the exact values for all the molecular models, including those with a structured liquid-vapor interface, if the clusters used for the estimates have more than about hundred molecules. The dependence on the constraining volume is found weak.