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Issue 12, 2010
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Ion association in low-polarity solvents: comparisons between theory, simulation, and experiment

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Abstract

The association of ions in electrolyte solutions at very low concentration and low temperature is studied using computer simulations and quasi-chemical ion-pairing theory. The specific case of the restricted primitive model (charged hard spheres) is considered. Specialised simulation techniques are employed that lead to efficient sampling of the arrangements and distributions of clusters and free ions, even at conditions corresponding to nanomolar solutions of simple salts in solvents with dielectric constants in the range 5–10, as used in recent experimental work on charged-colloid suspensions. A direct comparison is effected between theory and simulation using a variety of clustering criteria and theoretical approximations. It is shown that conventional distance-based cluster criteria can give erroneous results. A reliable set of theoretical and simulation estimators for the degree of association is proposed. The ion-pairing theory is then compared to experimental results for salt solutions in low-polarity solvents. The agreement is excellent, and on this basis some calculations are made for the screening lengths which will figure in the treatment of colloid-colloid interactions in such solutions. The accord with available experimental results is complete.

Graphical abstract: Ion association in low-polarity solvents: comparisons between theory, simulation, and experiment

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Publication details

The article was received on 25 Jan 2010, accepted on 22 Mar 2010 and first published on 13 May 2010


Article type: Paper
DOI: 10.1039/C001577F
Citation: Soft Matter, 2010,6, 2793-2800
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    Ion association in low-polarity solvents: comparisons between theory, simulation, and experiment

    C. Valeriani, P. J. Camp, J. W. Zwanikken, R. van Roij and M. Dijkstra, Soft Matter, 2010, 6, 2793
    DOI: 10.1039/C001577F

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