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Ion clustering in molecular dynamics simulations of sodium iodide solutions

journal contribution
posted on 01.10.1995, 00:00 authored by V Payne, J H Xu, Maria ForsythMaria Forsyth, M Ratner, D Shriver, S de Leeuw
Model systems of sodium iodide dissolved in dimethyl ether or 1,2-dimethoxyethane (glyme) were studied in order to investigate the structural and dynamic properties of ionic solutions in small and polymeric ethers. Full molecular dynamics simulations were performed at a range of different salt concentrations. An algorithm was designed which assigns ions to clusters and then calculates all the terms which contribute to ionic conductivity. In dilute solutions, free ions are the most common ionic species, followed by ion pairs. As the concentration increases, pairs become the most common species, with significant concentrations of clusters with 3 through 6 ions. Changing the solvent from dimethyl ether to glyme significantly decreases the ion clustering due to the chelate effect in which the two oxygens on a solvent stabilize an associated cation. The conductivity in stable systems is shown to be primarily the result of the movement of free ions and the relative movement of ions within neutral pairs. The Nernst-Einstein relation, commonly used in the discussion of polymer electrolytes, is shown to be inadequate to quantitatively describe conductivity in the model systems.

History

Journal

Electrochimica acta

Volume

40

Issue

13-14

Pagination

2087 - 2091

Publisher

Elsevier Science Pub. Co.

Location

New York, N.Y.

ISSN

0013-4686

eISSN

1873-3859

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

1995, Elsevier Science Ltd.