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

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
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 21; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
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