The Role of Coordination Number in Caging and Dynamical Heterogeneity

ABSTRACT

In this molecular dynamics simulation study, we investigate whether the instantaneous coordination number provides a simple, physically interpretable basis for decomposing local environments in the Kob–Andersen glass‐forming mixture. We show that coordination number partitions the system into sub‐populations with distinct dynamical, energetic, geometric, and temporal characteristics. Particles with intermediate coordination exhibit the slowest structural relaxation, the lowest per‐neighbor potential energy, and occupy the most geometrically distorted cages, demonstrating that the slowest, lowest‐energy cages are not the most isotropic. In contrast, under‐ and over‐coordinated environments represent distinct mobile populations with different coordination‐memory dynamics, suggesting that they relax through different microscopic pathways. The coordination‐memory function further reveals that the coordination number is a slow structural variable whose relaxation is coupled to the ‐relaxation process. These results demonstrate that conditioning on the instantaneous coordination number provides a transparent and physically interpretable decomposition of local environments, yielding systematic insight into the structural organization associated with dynamical heterogeneity.