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Accueil > Faits marquants > Bridging scales in disordered porous media by mapping molecular dynamics onto intermittent brownian motion

Bridging scales in disordered porous media by mapping molecular dynamics onto intermittent brownian motion

par Emilie Secret - 1er mars

Les travaux de Pierre Levitz, en collaboration avec Colin Bousige (Laboratoire des Multimatériaux et Interfaces, Lyon) et Benoit Coasne (LIPhy, Grenoble), sont parus récemment dans la revue Nature Communications. Ces travaux ont été sélectionnés pour apparaître dans la catégorie "Editor’s highlights" en chimie physique et inorganique.

Abstract :

Owing to their complex morphology and surface, disordered nanoporous media possess a rich diffusion landscape leading to specific transport phenomena. The unique diffusion mechanisms in such solids stem from restricted pore relocation and ill-defined surface boundaries. While diffusion fundamentals in simple geometries are well-established, fluids in complex materials challenge existing frameworks. Here, we invoke the intermittent surface/pore diffusion formalism to map molecular dynamics onto random walk in disordered media. Our hierarchical strategy allows bridging microscopic/mesoscopic dynamics with parameters obtained from simple laws. The residence and relocation times –tA,tB– are shown to derive from pore size d and temperature-rescaled surface interaction ε/kBT. tA obeys a transition state theory with a barrier ε/kBT and a prefactor 10−12s corrected for pore diameter d. tB scales with d which is rationalized through a cutoff in the relocation first passage distribution. This approach provides a formalism to predict any fluid diffusion in complex media using parameters available to simple experiments.