Large scale long-lived heterogeneity in the dynamics of supercooled liquids
The local mobility of particles in highly supercooled liquids is demonstrated to be spatially heterogeneous on time scales comparable to the structural relaxation time tau(alpha). The particle motions in the active regions dominantly contribute to the mean square displacement, giving rise to a diffusion constant systematically larger than the Stokes-Einstein value. The diffusion process eventually becomes homogeneous on time scales longer than the life time of the heterogeneity structure (similar to 3 tau(alpha)). The heterogeneity structure in the local mobility is very analogous to the critical fluctuation in Ising spin systems with their structure factor being excellently fitted to the Ornstein-Zernike form.
supercooled liquid glass transition kinetic heterogeneity shear flow molecular dynamics simulation