Mechanical disorder of sticky-sphere glasses. I. Effect of attractive interactions

TL;DR

This study reveals that attractive interactions significantly influence the elastic properties and disorder in glassy solids, challenging previous assumptions about their secondary role in dense liquids.

Contribution

It demonstrates how tuning attractive interactions in computer glasses alters mechanical disorder and stability, highlighting effects similar to thermal annealing and identifying a stabilization mechanism.

Findings

Increasing glass stickiness reduces mechanical disorder measures.

Strong attractions decrease soft, quasilocalized modes and their core size.

Stabilization arises mainly from depletion of negative stiffness interactions.

Abstract

Recent literature indicates that attractive interactions between particles of a dense liquid play a secondary role in determining its bulk mechanical properties. Here we show that, in contrast with their apparent unimportance to the bulk mechanics of dense liquids, attractive interactions can have a major effect on macro- and microscopic elastic properties of glassy solids. We study several broadly-applicable dimensionless measures of stability and mechanical disorder in simple computer glasses, in which the relative strength of attractive interactions -- referred to as `glass stickiness' -- can be readily tuned. We show that increasing glass stickiness can result in the decrease of various quantifiers of mechanical disorder, on both macro- and microscopic scales, with a pair of intriguing exceptions to this rule. Interestingly, in some cases strong attractions can lead to a reduction of the number density of soft, quasilocalized modes, by up to an order of magnitude, and to a substantial decrease in their core size, similar to the effects of thermal annealing on elasticity observed in recent works. Contrary to the behavior of canonical glass models, we provide compelling evidence indicating that the stabilization mechanism in our sticky-sphere glasses stems predominantly from the self-organized depletion of interactions featuring large, \emph{negative} stiffnesses. Finally, we establish a fundamental link between macroscopic and microscopic quantifiers of mechanical disorder, which we motivate via scaling arguments. Future research directions are discussed.