Molecular simulation of the surface tension of 33 multi-site models for real fluids

Molecular models of real fluids are validated by comparing the vapour-liquid surface tension from molecular dynamics (MD) simulation to correlations of experimental data. The considered molecular models consist of up to 28 interaction sites, including Lennard-Jones sites, point charges, dipoles, and quadrupoles. They represent 33 real fluids, such as ethylene oxide, sulfur dioxide, phosgene, benzene, ammonia, formaldehyde, methanol, and water, and were adjusted to reproduce the saturated liquid density, the vapour pressure, and the enthalpy of vaporization. The models were not adjusted to interfacial properties, however, so that the present MD simulations are a test of model predictions. It is found that all of the considered models overestimate the surface tension. In most cases, however, the relative deviation between the simulation results and correlations to experimental data is smaller than 20%. This observation corroborates the outcome of previous studies on the surface tension of two-centre Lennard-Jones plus point quadrupole (2CLJQ) and two-centre Lennard-Jones plus point dipole (2CLJD) fluid models, where an overestimation of the order of 10 to 20% was found.