Review and Comparison of Equations of State for the Lennard-Jones Fluid

Abstract

The Lennard-Jones (LJ) potential is widely used for describing simple fluids; it is also a point of departure for developing models of complex fluids. Thermodynamic properties of the LJ fluid have been studied by molecular simulations by many authors and a critical review of the available data, which comprises about 35,000 data points, has been published recently [J. Chem. Inf. Mod. 59 (2019) 4248–4265]. The importance of the LJ fluid has also triggered the development of a large number of equations of state (EOS). In the present work, 20 LJ EOS were critically assessed by comparing their results with consolidated data from computer experiments. A large variety of thermophysical properties was considered: vapor pressure; saturated densities; enthalpy of vaporization; critical properties; thermal, caloric, and entropic properties at homogeneous state points; and second and third virial coefficients. It was found that none of the available LJ EOS meets the following two criteria: (1) it does not yield unphysical artifacts when used for extrapolations, and (2) it describes data from computer experiments within their statistical uncertainty in most fluid regions. Furthermore, a re-parameterization of the monomer term of the PC-SAFT EOS was carried out by fitting it to data of the LJ fluid. The new LJ EOS yields good results for the LJ fluid, but does not outperform the best existing LJ EOS.