Bridging scales in disordered porous media by mapping molecular dynamics onto intermittent Brownian motion.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33589629.
- Also identified by DOI 10.1038/s41467-021-21252-x and PMC identifier 7884405.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
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<sub>A</sub>, t<sub>B</sub> - are shown to derive from pore size d and temperature-rescaled surface interaction ε/k<sub>B</sub>T. t<sub>A</sub> obeys a transition state theory with a barrier ~ε/k<sub>B</sub>T and a prefactor ~10<sup>-12</sup> s corrected for pore diameter d. t<sub>B</sub> 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.