Binary mixture of hard disks as a model glass former: Caging and uncaging

摘要

I have proposed a measure for the cage effect in glass forming systems. A binary mixture of hard disks is numerically studied as a model glass former. A network is constructed on the basis of the colliding pairs of disks. A rigidity matrix is formed from the isostatic (rigid) subnetwork, corresponding to a cage. The determinant of the matrix changes its sign when an uncaging event occurs. The time evolution of the number of uncaging events is determined numerically. I have found that there is a gap in the uncaging time scales between the cages involving different numbers of disks. Caging of one disk by two neighboring disks sustains for a longer time as compared with other cages involving more than one disk. This gap causes two-step relaxation of this system.