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.