Simultaneous description of bulk and interfacial properties of fluids by the Mie potential

TL;DR

This study systematically investigates the vapor-liquid equilibrium of Mie potentials with varying repulsive exponents using molecular simulation, deriving correction expressions and enabling optimized parameter fitting for real fluids like CO2.

Contribution

It introduces a comprehensive simulation framework for Mie fluids, including long-range corrections and a multicriteria optimization method for parameter fitting.

Findings

Consistent simulation results with existing literature.

Multicriteria optimization allows tailored parameter fitting.

Models can accurately predict multiple thermodynamic properties simultaneously.

Abstract

The vapor-liquid equilibrium (VLE) of the Mie potential, where the dispersive exponent is constant (m = 6) while the repulsive exponent n is varied between 9 and 48, is systematically investigated by molecular simulation. For systems with planar vapor-liquid interfaces, long-range correction expressions are derived, so that interfacial and bulk properties can be computed accurately. The present simulation results are found to be consistent with the available body of literature on the Mie fluid which is substantially extended. On the basis of correlations for the considered thermodynamic properties, a multicriteria optimization becomes viable. Thereby, users can adjust the three parameters of the Mie potential to the properties of real fluids, weighting different thermodynamic properties according to their importance for a particular application scenario. In the present work, this is demonstrated for carbon dioxide for which different competing objective functions are studied which describe the accuracy of the model for representing the saturated liquid density, the vapor pressure and the surface tension. It is shown that models can be found which describe simultaneously the saturated liquid density and vapor pressure with good accuracy, and it is discussed to what extent this accuracy can be upheld as the model accuracy for the surface tension is further improved.