Diffusion of interacting particles in discrete geometries

TL;DR

This paper derives analytical expressions for particle diffusion in a discrete chain with interactions, revealing conditions where self-diffusion exceeds transport diffusion, and validates findings with experimental data.

Contribution

It provides exact analytical formulas for diffusion in discrete geometries with interactions and compares them with experimental results, highlighting the role of free-energy concavity.

Findings

Self-diffusion can surpass transport diffusion with concave free-energy functions.

Analytical expressions match experimental data for ZIF-8.

Correlations influence diffusion behavior as shown by numerical results.

Abstract

We evaluate the self-diffusion and transport diffusion of interacting particles in a discrete geometry consisting of a linear chain of cavities, with interactions within a cavity described by a free-energy function. Exact analytical expressions are obtained in the absence of correlations, showing that the self-diffusion can exceed the transport diffusion if the free-energy function is concave. The effect of correlations is elucidated by comparison with numerical results. Quantitative agreement is obtained with recent experimental data for diffusion in a nanoporous zeolitic imidazolate framework material, ZIF-8.