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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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|
|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|
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