Nonconformal Interaction Models and Thermodynamics of Polar Fluids

Influence of molecular parameters on the representativeness of interfacial properties of simple fluids

New parameterizations for the Lennard-Jones 12/6 potential capable of reproducing the vapor pressure and surface tension with sufficient precision, but not the liquid-vapor equilibrium densities for the case of simple fluids that include Ar, Kr, Xe, Ne, and CH4 are presented in this work. These results are compared with those derived from the family of Mie(n, 6) potentials, which adequately reproduce the coexistence curve and the vapor pressure, leaving aside the surface tension. In addition, a detailed analysis is presented on different parameterizations and methodologies, which have been developed in recent decades to estimate the interfacial properties of interest here for simple fluids, such as argon, which is a molecule that is, in principle, "simple" to study but that clearly reveals the enormous discrepancy between the results reported in the literature throughout these years. These facts undoubtedly reveal one of the fundamental problems in the context of molecular thermodynamics of fluids: reproducing different thermodynamic properties with sufficient precision from a single set of free parameters for some interaction potential. In order to show the scope of the parameterizations presented for the Lennard-Jones model, they were successfully applied to the case of binary mixtures, which included Ar-Kr, Ar-CH4, and Xe-Kr. Finally, and with the aim of showing a possible solution to the problem posed in this research, results of the same interfacial properties above mentioned for argon and methane were presented in this work by using a set of molecular interactions, called ANC2s, whose flexibility allowed to reproduce the experimental evidence with just one parameterization. The results reported in this work were generated using molecular dynamics simulations.