Correlation between kinetic fragility and Poisson's ratio from analysis of data for soft colloids

TL;DR

This study investigates the relationship between fragility and elasticity in soft colloids, revealing a different correlation pattern compared to molecular glasses, and linking fluid structure to its dynamic behavior.

Contribution

It introduces a novel analysis connecting fragility indices with elastic properties in soft colloids using experimental data and theoretical modeling.

Findings

Fragility correlates with Poisson's ratio differently than in molecular glasses.

Elastic constants are fitted using pair correlation functions and interaction potentials.

The fluid structure significantly influences its dynamic fragility.

Abstract

We consider the link between fragility and elasticity that follows from analysis of the data for a set of soft-colloid materials consisting of deformable spheres reported by Mattsson et. al., in Nature vol 462, 83 (2009). Fragility index for a soft-colloid is obtained from the density dependence of the long time relaxation near a so-called glass transition point. In addition, we fit data for the high frequency shear modulus for the respective soft-colloid to a corresponding theoretical expression for the same modulus. This expression for the elastic constant is in terms of the corresponding pair correlation function for the liquid treated as of uniform density. The pair correlation function is adjusted through a proper choice of the parameters for the two body interaction potential for the respective soft-colloid material. The nature of correlation between the fragility and Poisson ratio observed for the soft colloids is qualitatively different, as compared to the same for molecular glasses. The observed link between fragility of a metastable liquid and its elastic coefficients is a manifestation of the effects of structure of the fluid on its dynamics.