Transition from Knudsen to molecular diffusion in activity of absorbing irregular interfaces

TL;DR

This study uses molecular dynamics to analyze how transport mechanisms transition from Knudsen to molecular diffusion at irregular interfaces, revealing changes in active zone length and supporting a simple random-walk model.

Contribution

It provides a detailed molecular dynamics analysis of the diffusion transition at irregular interfaces and introduces a simple random-walk model for qualitative understanding.

Findings

Active zone length decreases with density during transition

In the molecular diffusion limit, active zone length approaches system size

Random-walk model qualitatively describes diffusion features

Abstract

We investigate through molecular dynamics the transition from Knudsen to molecular diffusion transport towards 2d absorbing interfaces with irregular geometry. Our results indicate that the length of the active zone decreases continuously with density from the Knudsen to the molecular diffusion regime. In the limit where molecular diffusion dominates, we find that this length approaches a constant value of the order of the system size, in agreement with theoretical predictions for Laplacian transport in irregular geometries. Finally, we show that all these features can be qualitatively described in terms of a simple random-walk model of the diffusion process.