On the properties of methanolic NaCl solution by molecular dynamics simulations

Sanchez, Cruz; Domı́nguez, J.; Pizio,

doi:10.5488/cmp.23.23602

Cited by 1 publication

(1 citation statement)

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“…Furthermore, there is a downward shift in the corresponding MIACs where the Debye–Hückel limiting slope falls much more sharply at higher methanol contents. There are a few prior studies of the NaCl + water + methanol system using molecular dynamics (MD) simulations. − ,, However, these studies have been limited to structural and some transport properties, such as pair correlation functions, coordination numbers, and self-diffusion coefficients. None of these reported MIACs and salt solubilities, which are the focus of the current work.…”

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confidence: 99%

Activity Coefficients and Solubilities of NaCl in Water–Methanol Solutions from Molecular Dynamics Simulations

Saravi

Panagiotopoulos

2022

J. Phys. Chem. B

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We obtain activity coefficients and solubilities of NaCl in water–methanol solutions at 298.15 K and 1 bar from molecular dynamics (MD) simulations with the Joung–Cheatham, SPC/E, and OPLS-AA force fields for NaCl, water, and methanol, respectively. The Lorentz–Berthelot combining rules were adopted for the unlike-pair interactions of Na+, Cl–, and the oxygen site in SPC/E water, and geometric combining rules were utilized for the remainder of the cross interactions. We found that the selection of appropriate combining rules is important in obtaining physically realistic solubilities. The solvent compositions studied range from pure water to pure methanol. Several salt concentrations were investigated at each solvent composition, from the lowest concentrations permitted by the system size used up to the experimental solubilities. We first calculated individual ion activity coefficients (IIACs) for Na+ and Cl– from the free energy change due to the gradual insertion of a single cation or anion into the solution, accompanied by a neutralizing background. We obtained the salt solubilities by comparing the chemical potentials in solution with solid NaCl chemical potentials calculated previously using the Einstein crystal method. Mean ionic activity coefficients obtained from the IIACs are in reasonable agreement with experimental data, with deviations increasing for solutions of higher methanol content. Predictions for the salt solubility are in surprisingly good agreement with experimental data, despite well-known challenges in the simultaneous calculation of activity coefficients and solubilities with classical MD simulations. The present study demonstrates that good predictions for these two important phase equilibrium properties can be obtained for mixed-solvent electrolyte solutions using existing nonpolarizable models and further suggests that the previously proposed single ion insertion technique can be extended to complex mixed-solvent solutions as well.

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