Microcanonical-ensemble perturbation theory for thermodynamic and diffusion properties of square-well fluids

We present results for thermodynamic and diffusion properties of a square-well fluid (SW) using the Microcanonical-Ensemble perturbation theory (MEPT) [Mol. Phys. 116, 351 (2018)]. The aim of this work is to assess the accuracy of MEPT that is required in order to model real substances properties. We con-sider the extension of MEPT for binary mixtures of SW fluids, using the Lorentz-Berthelot combining rules. The phase behavior of binary square-well mixtures are studied, exploring in detail the influence of the hard-core size ratios, dispersion energy ratios, and variable attractive range potential. Excellent agreement between the MEPT approach and Gibbs Ensemble Monte Carlo (GEMC) simulation is found, for a wide range of temperatures and compositions. The relevance of perturbation terms of order higher than two is also considered, comparing with SAFT-VR results. This approach is a first step in modeling inhomogeneous systems, such as adsorption and interfacial properties of binary mixtures based on dis-crete potential systems as reference fluids.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study presents the thermodynamic and diffusion properties of a square-well fluid using Microcanonical-Ensemble perturbation theory (MEPT). It assesses the accuracy of MEPT for modeling real substances and investigates the phase behavior of binary square-well mixtures. The results show excellent agreement between MEPT and Gibbs Ensemble Monte Carlo simulation, highlighting the relevance of higher-order perturbation terms and the potential for modeling inhomogeneous systems.