Issue 29, 2022

Density functional theory for the prediction of interfacial properties of molecular fluids within the SAFT-γ coarse-grained approach

Abstract

Recently, we have proposed the SAFT-VR Mie MF DFT approach [Algaba et al., Phys. Chem. Chem. Phys., 2019, 21, 11937–11948] to investigate systems that exhibit fluid–fluid interfaces. This formalism is based on the combination of the Statistical Associating Fluid Theory for attractive potentials of variable range using Mie intermolecular potential (SAFT-VR Mie) and a Density Functional Theory (DFT) treatment of the free energy. A mean-field approach is used to evaluate the attractive term, neglecting the pair correlations associated to attractions. This theory has been combined with reported SAFT-γ Coarse-Grained (CG) Mie force fields to provide an excellent description of the vapor–liquid interface of carbon dioxide and water pure fluids. The present work is a natural and necessary extension of this previous study. We assess the adequacy of the proposed methodology for dealing with inhomogeneous fluid systems of large complex molecules, in particular carbon tetrafluoride and sulfur hexafluoride greenhouse gases, the refrigerant 2,3,3,3-tetrafluoro-1-propene, and the long-chain n-decane and n-eicosane hydrocarbons. The obvious diversity of these fluids, their chemical and industrial interest, and the fact of that SAFT-γ CG Mie force fields have been reported for them justify such choice. With the aim of testing the theory, we perform Molecular Dynamics simulations in the canonical ensemble using the direct coexistence technique for the same models. We focus both on bulk, such as coexistence diagrams and vapor pressure curves, as well as interfacial properties, including surface tension. The comparison of the theoretical predictions with the computational results as well as with experimental data taken from the literature demonstrates the reliability and generalization of this method for dealing simultaneously with vapor–liquid equilibrium and interfacial phenomena. Hence, it appears as a potential tool for the interface analysis, with the main advantage over molecular simulation of low computational cost, and solving the experimental difficulties in accurately measuring the surface tension of certain systems.

Graphical abstract: Density functional theory for the prediction of interfacial properties of molecular fluids within the SAFT-γ coarse-grained approach

Article information

Article type
Paper
Submitted
03 Apr 2022
Accepted
16 Jun 2022
First published
29 Jun 2022
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2022,12, 18821-18833

Density functional theory for the prediction of interfacial properties of molecular fluids within the SAFT-γ coarse-grained approach

J. Algaba, B. Mendiboure, P. Gómez-Álvarez and F. J. Blas, RSC Adv., 2022, 12, 18821 DOI: 10.1039/D2RA02162E

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