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

Colin Bousige (1) , Pierre Levitz (2) , Benoit Coasne (3)

1 LMI - Laboratoire des Multimatériaux et Interfaces
2 PHENIX - PHysicochimie des Electrolytes et Nanosystèmes InterfaciauX
3 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]

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 timest A , t Bare shown to derive from pore size d and temperature-rescaled surface interaction ε/k B T. t A obeys a transition state theory with a barrier~ε/k B T and a prefactor~10 −12 s corrected for pore diameter d. t B 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.

Domaines: Physique [physics]; Chimie théorique et/ou physique; Science des matériaux [cond-mat.mtrl-sci]

Colin Bousige, Pierre Levitz, Benoit Coasne. Bridging scales in disordered porous media by mapping molecular dynamics onto intermittent Brownian motion. Nature Communications, 2021, 12 (1), pp.1043. ⟨10.1038/s41467-021-21252-x⟩. ⟨hal-03141574⟩