Using Available Volume to Predict Fluid Diffusivity in Random Media

TL;DR

This paper introduces a simple predictive equation for fluid diffusivity in quenched-annealed systems, emphasizing the critical role of available volume in determining mobility, even when static correlations are similar.

Contribution

The study presents a novel, volume-based predictive equation for fluid diffusivity in random media, applicable to different matrix types and capturing mobility differences.

Findings

The equation accurately predicts diffusivity across various matrix types.

Available volume is a key factor influencing fluid mobility.

The model accounts for large mobility differences with similar static correlations.

Abstract

We propose a simple equation for predicting self-diffusivity of fluids embedded in random matrices of identical, but dynamically frozen, particles (i.e., quenched-annealed systems). The only nontrivial input is the volume available to mobile particles, which also can be predicted for two common matrix types that reflect equilibrium and non-equilibrium fluid structures. The proposed equation can account for the large differences in mobility exhibited by quenched-annealed systems with indistinguishable static pair correlations, illustrating the key role that available volume plays in transport.