D. Caprion, M. Kluge, J. Matsui, and H.R. Schober

Heterogeneity in super-cooled liquids and glasses is studied using the non-Gaussianity parameter. We simulate selenium and a binary Lennard-Jones system by molecular dynamics. In the non-Gaussianity three time domains can be distinguished: an increase on the ps-scale due to the vibrational (ballistic) motion of the atoms, followed by a growth, due to local relaxations (ß-relaxation ) at not too high temperatures and finally a slow drop at long times. The non-Gaussianity follows in the ß-regime a SQR(t)-law which can be explained by collective hopping.