Programme

P.76 -- Posters, VCTP-51

Date: Thursday, 6 August 2026

Time: 09:30 - 10:30

A New Set of Combining Rules for the Mie (λ, 6) Potential for Predicting Thermophysical Properties of Fluid Mixtures

Nguyen Van Phuoc, Thanh Doanh Le, Van Hoa Nguyen, Suresh Alapati, Stéphanie Delage Santacreu, Guillaume Galliéro, and Hai Hoang

Trường ĐH Tôn Đức Thắng

Accurate prediction of thermophysical properties of fluid mixtures is essential for chemical engineering, petroleum engineering, separation processes, and supercritical-fluid applications [1]. Molecular simulation provides a powerful route for predicting such properties when experimental data are limited or difficult to obtain [2]. Among molecular models, force fields based on the Mie (λ, 6) potential have attracted increasing interest because they offer greater flexibility than the Lennard-Jones potential by explicitly tuning the repulsive exponent. These models have been successfully applied to pure fluids and mixtures, especially within coarse-grained molecular simulation frameworks [3,4]. However, the predictive capability of Mie-based force fields for mixtures strongly depends on the accuracy of unlike interaction parameters, which are usually estimated from pure-component parameters using combining rules. In this work, a new set of combining rules is proposed for the Mie (λ, 6) potential. The derivation is based on a distortion model for the repulsive contribution and a geometric mean approximation for the attractive contribution [5], in conjunction with first-order mathematical approximations. The resulting expressions provide the unlike repulsive exponent, collision diameter, and potential well depth directly from pure-component Mie parameters, without introducing additional adjustable binary parameters. The proposed combining rules were evaluated for a broad range of systems, from simple monoatomic to more complex molecular mixtures, using Monte Carlo simulations. Their predictive performance was assessed using several thermodynamic properties that are sensitive to unlike interactions, including Henry’s law constants, pressure–composition phase diagrams, and excess molar volumes. For mixtures whose components have comparable Mie parameters, the new rules yield predictions similar to those obtained with existing combining rules. However, for highly asymmetric systems, they provide substantially better agreement with experimental data. These results indicate that the proposed rules offer a more reliable and transferable approach for predicting thermophysical properties of fluid mixtures without requiring additional binary parameter fitting. Keywords: Mie (λ, 6) potential; combining rules; molecular simulation; phase equilibrium; Henry’s law constant; excess molar volume. Keywords: Mie (λ, 6) potential; combining rules; molecular simulation; phase equilibrium; Henry’s law constant; excess molar volume. References [1] G. M. Kontogeorgis et al., Ind. Eng. Chem. Res., 60, 4987–5013, 2021. [2] M. J. Tillotson et al., Phys. Chem. Chem. Phys., 25, 12607–12628, 2023. [3] A. Mejía et al., Ind. Eng. Chem. Res., 53, 4131–4141, 2014. [4] H. Hoang et al., Ind. Eng. Chem. Res., 56, 9213–9226, 2017. [5] C. L. Kong, J. Chem. Phys., 59, 2464–2467, 1973.

Presenter: Nguyen Van Phuoc