Enhanced Diffusion of a Needle in a Planar Course of Point Obstacles

TL;DR

This study investigates the diffusion behavior of a needle in a dense obstacle field, revealing a divergence in diffusion coefficient and new dynamic phenomena such as zig-zag motion and non-Gaussian behavior.

Contribution

It introduces a novel understanding of needle diffusion in dense media, highlighting a divergence in diffusion coefficient and associated dynamic features.

Findings

Diffusion coefficient diverges with a power law exponent of ~0.8

Transport becomes faster at higher densities

Zig-zag motion and non-Gaussian behavior observed

Abstract

The transport of an infinitely thin, hard rod in a random, dense array of point obstacles is investigated by molecular dynamics simulations. Our model mimics the sterically hindered dynamics in dense needle liquids. The center-of-mass diffusion exhibits a minimum, and transport becomes increasingly fast at higher densities. The diffusion coefficient diverges according to a power law in the density with an approximate exponent of 0.8. This observation is connected with a new divergent time scale, reflected in a zig-zag motion of the needle, a two-step decay of the velocity-autocorrelation function, and a negative plateau in the non-Gaussian parameter.