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Updated: Aug 8, 2026

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
Published on: September 26, 2016
Ion dynamics in compacted clays: derivation of a two-state diffusion-reaction scheme from the lattice Fokker-Planck
B Rotenberg1, J-F Dufre Che, B Bagchi
1UMR 7612, Laboratoire LI2C, Université Pierre et Marie Curie--Paris 6, Case Courrier 51, 4 Place Jussieu, Paris F-75005, France. rotenber@ccr.jussieu.fr
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.
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