Rejuvenation in Deep Thermal Cycling of a Generic Model Glass: A Study of Per-Particle Energy Distribution.

Marian Bruns,Fathollah Varnik

doi:10.3390/ma15030829

Abstract

We investigate the effect of low temperature (cryogenic) thermal cycling on a generic model glass and observe signature of rejuvenation in terms of per-particle potential energy distributions. Most importantly, these distributions become broader and its average values successively increase when applying consecutive thermal cycles. We show that linear dimension plays a key role for these effects to become visible, since we do only observe a weak effect for a cubic system of roughly one hundred particle diameter but observe strong changes for a rule-type geometry with the longest length being two thousand particle diameters. A consistent interpretation of this new finding is provided in terms of a competition between relaxation processes, which are inherent to glassy systems, and excitation due to thermal treatment. In line with our previous report (Bruns et al., PRR 3, 013234 (2021)), it is shown that, depending on the parameters of thermal cycling, rejuvenation can be either too weak to be detected or strong enough for a clear observation.

Highlights

When cooled below their glass transition temperature Tg, metallic glasses (MGs), alike other amorphous solids, undergo structural relaxation approaching an unreachable equilibrium state [1]
We have investigated the effect of low temperature thermal cycling on per-particle energy distribution of a standard model glass, the well-known 80:20 binary Lennard-Jones mixture, first introduced by Kob and Andersen in their seminal work [26,27]
The possibility of rejuvenation of the glassy state upon a cyclic temperature variation well below the glass transition point but had only found that rejuvenation processes were not strong enough to stop or reverse aging but could only slow it down. This observation was corroborated on a qualitative level by calorimetry experiments on bulk metallic glasses

Summary

Introduction

When cooled below their glass transition temperature Tg , metallic glasses (MGs), alike other amorphous solids, undergo structural relaxation approaching an unreachable equilibrium state [1]. Since a cubic geometry makes such an undertaking computationally prohibitively expensive, we have resorted to a slab-shaped geometry This choice is encouraged by our previous study, where the use of a long linear dimension was found to be instrumental in unrevealing the spatially slowly varying structural heterogeneity, which occurs on the scale of many hundreds particle diameters [25]. This approach proves effective in revealing strong rejuvenation effects upon deeptemperature cycling regarding per-particle energy distribution. A conclusion and outlook compiles our most important findings and closes this manuscript

Computational Details

Thermal Treatment

Results

Conclusions and Outlook