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Title: Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions

Abstract

Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. The purely ionic contribution to the dielectric response is negligible, but determines the conductivity of the salt solutions. The ion-water cross correlation contribution is negative and reduces the total dielectric response by about 5%-10% for 1 M solutions. The dominating water dielectric response is decomposed into different water solvation shells and ion-pair configurations, by this the spectral blue shift and the dielectric decrement of salt solutions with increasing salt concentration is demonstrated to be primarily caused by first-solvation shell water. With rising salt concentration the simulated spectra show more pronounced deviations from a single-Debye form and can be well described by a Cole-Cole fit, in quantitative agreement with experiments. Our spectral decomposition into ionic and different water solvation shell contributions does not render the individual contributions more Debye-like, this suggests the non-Debye-like character of the dielectric spectra of salt solutions not to be due to the superpositionmore » of different elementary relaxation processes with different relaxation times. Rather, the non-Debye-like character is likely to be an inherent spectral signature of solvation water around ions.« less

Authors:
;  [1];  [2]
  1. Fachbereich Physik, Freie Universität Berlin, 14195 Berlin (Germany)
  2. Physikalisches Institut, Universität Bayreuth, 95440 Bayreuth (Germany)
Publication Date:
OSTI Identifier:
22413272
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 141; Journal Issue: 21; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AQUEOUS SOLUTIONS; DECOMPOSITION; DIELECTRIC MATERIALS; IONS; MOLECULAR DYNAMICS METHOD; PERMITTIVITY; SALTS; SHELLS; SIMULATION; SODIUM BROMIDES; SODIUM CHLORIDES; SODIUM FLUORIDES; SODIUM IODIDES; SOLVATION; SPECTRA; WATER

Citation Formats

Rinne, Klaus F., Netz, Roland R., and Gekle, Stephan. Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions. United States: N. p., 2014. Web. doi:10.1063/1.4901927.
Rinne, Klaus F., Netz, Roland R., & Gekle, Stephan. Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions. United States. doi:10.1063/1.4901927.
Rinne, Klaus F., Netz, Roland R., and Gekle, Stephan. Sun . "Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions". United States. doi:10.1063/1.4901927.
@article{osti_22413272,
title = {Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions},
author = {Rinne, Klaus F. and Netz, Roland R. and Gekle, Stephan},
abstractNote = {Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. The purely ionic contribution to the dielectric response is negligible, but determines the conductivity of the salt solutions. The ion-water cross correlation contribution is negative and reduces the total dielectric response by about 5%-10% for 1 M solutions. The dominating water dielectric response is decomposed into different water solvation shells and ion-pair configurations, by this the spectral blue shift and the dielectric decrement of salt solutions with increasing salt concentration is demonstrated to be primarily caused by first-solvation shell water. With rising salt concentration the simulated spectra show more pronounced deviations from a single-Debye form and can be well described by a Cole-Cole fit, in quantitative agreement with experiments. Our spectral decomposition into ionic and different water solvation shell contributions does not render the individual contributions more Debye-like, this suggests the non-Debye-like character of the dielectric spectra of salt solutions not to be due to the superposition of different elementary relaxation processes with different relaxation times. Rather, the non-Debye-like character is likely to be an inherent spectral signature of solvation water around ions.},
doi = {10.1063/1.4901927},
journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 21,
volume = 141,
place = {United States},
year = {2014},
month = {12}
}