Publication dans Nature Communications

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

Publication dans Nature Communications

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

Félicitations à Colin Bousige du LMI, qui, avec ses collègues Benoît Coasne (LiPhy, Grenoble) et Pierre Levitz (PHENIX, Paris), vient de publier un article dans la revue “Nature Communications”, intitulé: “ Bridging scales in disordered porous media by mapping molecular dynamics onto intermittent Brownian motion”.

La diffusion des fluides dans des géométries nanoporeuses complexes représente un défi pour les approches de modélisation. Les auteurs décrivent ici la diffusivité macroscopique d’un fluide simple dans des matériaux nanoporeux désordonnés en établissant un pont entre les dynamiques microscopique et mésoscopique au moyen de paramètres obtenus à partir de lois physiques simples.

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 – $t_A$, $t_B$ – are shown to derive from pore size $d$ and temperature-rescaled surface interaction $\varepsilon/k_{\textrm{B}}T$. $t_A$ obeys a transition state theory with a barrier $\sim \varepsilon/k_{\textrm{B}}T$ and a prefactor $\sim 10^{-12}$ 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.

Pages liées