Unraveling molecular mechanisms of aging dynamics in the Kob–Andersen model: the role of free volume†

Abstract

This study elucidates the role of free volume in the aging dynamics of the Kob–Andersen (KA) model through temperature cycling experiments. By examining the relationship between free volume and key phenomena such as aging, rejuvenation, and memory effects, we clarify how free volume influences the aging process in this system. Our results reveal a strong correlation between local free volume and the fraction of fast-moving particles, both of which significantly affect the dynamic susceptibility. This indicates that aging dynamics are largely governed by rapidly relaxing particles residing in regions of larger local free volume. Notably, we find no evidence of rejuvenation effects, in contrast to previous reports on the Weeks–Chandler–Andersen (WCA) system; however, memory effects are observed and attributed to minimal local structural rearrangements during aging. Taken together, these findings contribute to a more detailed molecular-level understanding of aging dynamics and provide valuable perspectives on the complex behavior of glassy systems.