Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 14: Poster: Glasses I (jointly with DY)

CPP 14.13: Poster

Dienstag, 27. März 2012, 18:15–20:15, Poster A

Space-time phase transition in an atomistic model of glass formers — •Thomas Speck — Institut für Theoretische Physik II, Heinrich-Heine-Universität Düsseldorf, Germany

The transformation of a liquid into a solid crystal is a first-order phase transition that occurs through nucleation. All liquids can, therefore, be supercooled to a certain degree; and some turn into highly viscous, 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 activity persist. Here we study ensembles of trajectories for a popular atomistic glass former, the Kob-Andersen binary Lennard-Jones mixture. We characterize mobility in a single trajectory through the number of particles that undergo a long-lived displacement. These excited particles record the underlying excitations that lead to dynamic heterogeneity. Using umbrella sampling we determine the probability distribution of this order parameter and show that it is non-concave. This can be interpreted as a phase transition in space-time between an active, liquid-like phase and an inactive, jammed phase in which the system remembers its initial conditions over the observation time. Structural and dynamical properties of these two distinct dynamic phases are analyzed and consequences for the glass transition are discussed.