8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P8.54Thu 811:10-14:00Activity in supercooled dense liquidsThomas Speck 11 Institut für Theoretische Physik II, Universitätsstr. 1, Heinrich-Heine-UniversitätDüsseldorf 40225, Düsseldorf, GermanyThe transformation of a liquid into a solid crystal is a first-order phase transition that occurs throughnucleation. All liquids can, therefore, be supercooled to a certain degree; and some turn into highlyviscous, amorphous solids. One of the striking features is the emergence of dynamic heterogeneity,i.e., while overall particle motion becomes more and more restricted small regions of activitypersist. We study ensembles of trajectories for an atomistic glass former, the Kob-Andersen binaryLennard-Jones mixture, generated through molecular dynamics simulations. Activity is measuredbased on the overlap of particles with their initial positions in a given time window. Using umbrellasampling we determine the probability distribution of the activity and show that it is bimodal.This can be interpreted as two phases, an active, liquid-like phase and an inactive, jammed phasein which the system remembers its initial conditions over the observation time. Structural anddynamical properties of these two phases are analyzed.54