A thermodynamic unification of jamming

TL;DR

This paper introduces a thermodynamic framework to understand jamming in granular and molecular systems, linking structural aging, shear effects, and entropy without free parameters.

Contribution

It presents a novel thermodynamic model that unifies jamming phenomena across different materials using pressure, temperature, and free-volume concepts.

Findings

Predicts the jamming threshold via a non-thermal temperature.

Successfully models entropic data of molecular glasses.

Explains shear-banding and shear-softening mechanisms.

Abstract

Fragile materials ranging from sand to fire-retardant to toothpaste are able to exhibit both solid and fluid-like properties across the jamming transition. Unlike ordinary fusion, systems of grains, foams and colloids jam and cease to flow under conditions that still remain unknown. Here we quantify jamming via a thermodynamic approach by accounting for the structural ageing and the shear-induced compressibility of dry sand. Specifically, the jamming threshold is defined using a non-thermal temperature that measures the 'fluffiness' of a granular mixture. The thermodynamic model, casted in terms of pressure, temperature and free-volume, also successfully predicts the entropic data of five molecular glasses. Notably, the predicted configurational entropy avoids the Kauzmann paradox entirely. Without any free parameters, the proposed equation-of-state also governs the mechanism of shear-banding and the associated features of shear-softening and thickness-invariance.