Emergence of Intermediate Range Order in Jammed Packings

TL;DR

This study reveals the emergence of intermediate range order in jammed sphere packings, characterized by a prepeak in the structure factor that correlates with local coordination fluctuations and varies with friction and preparation history.

Contribution

It demonstrates the structural signature of intermediate range order in jammed packings and links it to local coordination fluctuations, highlighting the influence of friction and packing protocol.

Findings

Prepeak in structure factor indicates intermediate range order.

Prepeak growth correlates with increased friction.

Preparation history affects large-scale structural properties.

Abstract

We perform a structural analysis of large scale jammed packings of monodisperse, frictionless and frictional spheres to elucidate structural signatures of the static structure factor in the low-to-intermediate wavenumber ($q$) region. We employ discrete element method simulations containing up to eighty million particles, in which the particle friction coefficient(s), including sliding, rolling, and twisting interactions, are varied. At intermediate $q$ values, corresponding to length scales that lie between that of the nearest neighbor primary peak and the system size, we find the emergence of a prepeak -- a signature of intermediate range order -- that grows with increasing friction. We correlate the emergence of this peak to real space fluctuations in the local particle coordination number, which exhibits a grainy fluctuating field throughout the packing process that is retained in the final, mechanically stable state. While the formation of the prepeak shows varying degrees of robustness to packing protocol changes, our results suggest that preparation history may be used to construct packings with variable large length scale structural properties.