The contribution of the ion-ion and ion-solvent interactions in a molecular thermodynamic treatment of electrolyte solutions
OA Location
Author(s)
Type
Journal Article
Abstract
Developing molecular equations of state to treat electrolyte solutions is challenging due to the long-range nature of the Coulombic interactions. Seminal approaches commonly used are the mean spherical approximation (MSA) and the Debye–Hückel (DH) theory to account for ion–ion interactions and, often, the Born theory of solvation for ion–solvent interactions. We investigate the accuracy of the MSA and DH approaches using each to calculate the contribution of the ion–ion interactions to the chemical potential of NaCl in water, comparing these with newly computer-generated simulation data; the ion–ion contribution is isolated by selecting an appropriate primitive model with a Lennard-Jones force field to describe the solvent. A study of mixtures with different concentrations and ionic strengths reveals that the calculations from both MSA and DH theories are of similar accuracy, with the MSA approach resulting in marginally better agreement with the simulation data. We also demonstrate that the Born theory provides a good qualitative description of the contribution of the ion–solvent interactions; we employ an explicitly polar water model in these simulations. Quantitative agreement up to moderate salt concentrations and across the relevant range of temperature is achieved by adjusting the Born radius using simulation data of the free energy of solvation. We compute the radial and orientational distribution functions of the systems, thereby providing further insight on the differences observed between the theory and simulation. We thus provide rigorous benchmarks for use of the MSA, DH, and Born theories as perturbation approaches, which will be of value for improving existing models of electrolyte solutions, especially in the context of equations of state.
Date Issued
2022-12-01
Date Acceptance
2022-08-12
Citation
Journal of Physical Chemistry B, 2022, 126 (47), pp.9821-9839
ISSN
1520-6106
Publisher
American Chemical Society
Start Page
9821
End Page
9839
Journal / Book Title
Journal of Physical Chemistry B
Volume
126
Issue
47
Copyright Statement
Copyright © 2022 The Authors. Published by American Chemical Society. This publication is licensed under CC-BY 4.0 .
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/36395498
Subjects
ACTIVITY-COEFFICIENTS
ASSOCIATING FLUID THEORY
BORN MODEL
Chemistry
Chemistry, Physical
EQUATION-OF-STATE
FORCE-FIELD
FREE-ENERGY CALCULATIONS
MEAN SPHERICAL APPROXIMATION
MONTE-CARLO
Physical Sciences
PRIMITIVE MODEL
SAFT-VR PLUS
Science & Technology
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2022-11-17