Beyond the mean-field approximation for pair correlations in classical density functional theory: reference inhomogeneous non-associating monomeric fluids for use with SAFT-VR Mie DFT
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Published version
Author(s)
Bernet, Thomas
Ravipati, Srikanth
cárdenas, harry
Muller, Erich
Jackson, George
Type
Journal Article
Abstract
A free-energy functional is presented to explicitly take into account pair correlations between molecules in inhomogeneous fluids. The framework of classical density functional theory (DFT) is used to describe the variation in the density of molecules interacting through a Mie (generalized Lennard-Jones) potential. Grand Canonical Monte Carlo simulations are performed for the systems to validate the new functional. The statistical associating fluid theory developed for Mie fluids (SAFT-VR Mie) is selected as a reference for the homogeneous bulk limit of the DFT and is applied here to systems of spherical non-associating particles. The importance of a correct description of the pair correlations for a reliable representation of the free energy in the development of the equation of state is duly noted. Following the Barker–Henderson high-temperature expansion, an analogous formulation is proposed from the general DFT formalism to develop an inhomogeneous equivalent of the SAFT-VR Mie free energy as a functional of the one-body density. In order to make use of this new functional in adsorption studies, a non-local version of the DFT is considered, with specific weighted densities describing the effects of neighboring molecules. The computation of these quantities is possible in three-dimensional space for any pore geometry with repulsive or attractive walls. We showcase examples to validate the new functional, revealing a very good agreement with molecular simulation. The new SAFT-DFT approach is well-adapted to describe realistic complex fluids.
Date Issued
2024-09-07
Date Acceptance
2024-08-14
Citation
Journal of Chemical Physics, 2024, 161 (9)
ISSN
0021-9606
Publisher
American Institute of Physics
Journal / Book Title
Journal of Chemical Physics
Volume
161
Issue
9
Copyright Statement
© 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license
(http://creativecommons.org/licenses/by/4.0/).
(http://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
https://pubs.aip.org/aip/jcp/article/161/9/094115/3311234/Beyond-the-mean-field-approximation-for-pair
Publication Status
Published
Article Number
094115
Date Publish Online
2024-09-05