Coupling between Jump Motions and Correlated Motions

Abstract

We have studied the α and β relaxations of the generalized susceptibility (imaginary part of χ) for a two dimensional model fluid which contains 10,000 atoms via molecular dynamics (MD) simulation. We have found that jump motions and correlated motions of atoms exist in supercooled liquid state and glass state, and these two motions contribute to α and β peak of χ″, respectively. Highly correlated areas extend over hundreds of atoms in glass state. These motions are coupled strongly in glass state, and become stronger than in supercooled liquid state. This suggests that linearly correlated jump motions which change the neighborhood configuration occur in glass state, and this type of motion possibly becomes a main factor of the system relaxation.