Ion dynamics in compacted clays: Derivation of a two-state diffusionreaction scheme from the lattice Fokker-Planck equation

Rotenberg, B and Dufreche, JF and Bagchi, B and Giffaut, E and Hansen, JP and Turq, P (2006) Ion dynamics in compacted clays: Derivation of a two-state diffusionreaction scheme from the lattice Fokker-Planck equation. In: Journal Of Chemical Physics, 124 (15). 154701-1-154701-12.

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Abstract

We show how a two-state diffusion-reaction description of the mobility of ions confined within compacted clays can be constructed from the microscopic dynamics of ions in an external field. The diffusion-reaction picture provides the usual interpretation of the reduced ionic mobility in clays, but the required partitioning coefficient K-d between trapped and mobile ions is generally an empirical parameter. We demonstrate that it is possible to obtain K-d from the microscopic dynamics of ions interacting with the clay surfaces by evaluating the ionic mobility using a novel lattice implementation of the Fokker-Planck equation. The resulting K-d allows a clear-cut characterization of the trapping sites on the clay surfaces and determines the adsorption/desorption rates. The results highlight the limitations of standard approximation schemes and pinpoint the crossover from jump to Brownian diffusion regimes.

Item Type:	Journal Article
Publication:	Journal Of Chemical Physics
Publisher:	American Institute Of Physics
Additional Information:	Copyright of this article belongs to American Institute Of Physics.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	31 Mar 2009 04:27
Last Modified:	19 Sep 2010 04:57
URI:	http://eprints.iisc.ac.in/id/eprint/17630

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