Free energy of solvation of simple ions: Molecular-dynamics study of solvation of Cl- and Na+ in the ice/water interface

Title
Free energy of solvation of simple ions: Molecular-dynamics study of solvation of Cl- and Na+ in the ice/water interface
Publication Date
2005
Author(s)
Smith, Erica
( author )
OrcID: https://orcid.org/0000-0002-8090-4768
Email: esmith32@une.edu.au
UNE Id une-id:esmith32
Bryk, Taras
Haymet, Anthony D J
Type of document
Journal Article
Language
en
Entity Type
Publication
Publisher
AIP Publishing LLC
Place of publication
United States of America
DOI
10.1063/1.1953578
UNE publication id
une:8274
Abstract
Molecular-dynamics simulations of Cl- and Na+ ions are performed to calculate ionic solvation free energies in both bulk simple point-charge/extended water and ice 1 h at several different temperatures, and at the basal ice 1 h/water interface. For the interface we calculate the free energy of "transfer" of the ions across the ice/water interface. For the ions in bulk water in the NPT ensemble at 298 K and 1 atm, results are found to be in good agreement with experiments, and with other simulation results. Simulations performed in the NVT ensemble are shown to give equivalent solvation free energies, and this ensemble is used for the interfacial simulations. Solvation free energies of Cl− and Na+ ions in ice at 150 K are found to be ~ 30 and ~ 20 kcal mol⁻¹, respectively, less favorable than for water at room temperature. Near the melting point of the model the solvation of the ions in water is the same (within statistical error) as that measured at room temperature, and in the ice is equivalent and ~ 10 kcal mol⁻¹ less favorable than the liquid. The free energy of transfer for each ion across ice/water interface is calculated and is in good agreement with the bulk observations for the Cl- ion. However, for the model of Na+ the long-range electrostatic contribution to the free energy was more negative in the ice than the liquid, in contrast with the results observed in the bulk calculations.
Link
Citation
The Journal of Chemical Physics, 123(3), p. 1-16
ISSN
1089-7690
0021-9606
1520-9032
Start page
1
End page
16

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