Anomalous Behavior of the Diffusion Coefficient in Interacting Adsorbates

TL;DR

This study uses Langevin simulations to explore how diffusion coefficients of interacting adsorbates vary with friction, revealing anomalous behaviors at low friction and potential-dependent effects.

Contribution

It uncovers the anomalous diffusion behavior of tracer and bulk diffusion coefficients in low friction regimes, especially with coupled potentials, and shows potential-dependent reversals.

Findings

Anomalous diffusion observed at low friction in coupled potentials.

Diffusion exponents depend on the specific potentials used.

Potential modifications can revert anomalous diffusion to normal.

Abstract

Langevin simulations provide an effective way to study collective effects of Brownian particles immersed in a two-dimensional periodic potential. In this paper, we concentrate essentially on the behaviour of the tracer (DTr) and bulk (DB) diffusion coefficients as function of friction. Our simulations show that in the high friction limit, the two physical quantities DTr and DB present qualitatively the same behaviour, for both coupled and decoupled substrate potentials. However, for the low friction regime, and especially for the coupled potential case, an anomalous diffusion behaviour is found. We also found that in the case of weak dynamical coupling between the ad-particles and the substrate, the exponents are not universal and rather depend on the potentials. Moreover, changes in the inter-particle potentials may reverse the behaviour to a normal one.