Conduction in jammed systems of tetrahedra

TL;DR

This paper investigates how the shape of grains, specifically tetrahedra, affects electrical conduction in jammed systems, revealing unique conduction pathways and providing insights for designing advanced nanomaterials.

Contribution

It demonstrates that tetrahedral packings have distinct conduction mechanisms compared to sphere packings, with implications for nanomaterial development.

Findings

Tetrahedral packings show different conduction pathways than sphere packings.

Granular constrictions lead to short-range temperature distortions.

Effective medium theory predicts conductivity within 10% at jamming.

Abstract

Control of transport processes in composite microstructures is critical to the development of high performance functional materials for a variety of energy storage applications. The fundamental process of conduction and its control through the manipulation of granular composite attributes (e.g., grain shape) are the subject of this work. We show that athermally jammed packings of tetrahedra with ultra-short range order exhibit fundamentally different pathways for conduction than those in dense sphere packings. Highly resistive granular constrictions and few face-face contacts between grains result in short-range distortions from the mean temperature field. As a consequence, 'granular' or differential effective medium theory predicts the conductivity of this media within 10% at the jamming point; in contrast, strong enhancement of transport near interparticle contacts in packed-sphere composites results in conductivity divergence at the jamming onset. The results are expected to be particularly relevant to the development of nanomaterials, where nanoparticle building blocks can exhibit a variety of faceted shapes.