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Regensburg 2019 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 54: Poster: Complex, Fluids, Glasses, Granular

DY 54.5: Poster

Thursday, April 4, 2019, 15:00–18:00, Poster B2

Thermodynamic bond-angular instability drives glass formation — •Andrii Babich1,2, Maria Göbel1,5, Volodymyr Bugaev2,3, Johannes Roth3, Gerhard Grübel1,4, and Peter Wochner21Center for Ultrafast Imaging,University of Hamburg — 2Max Planck Institute for Solid State Research, Stuttgart — 3Institute for Functional Matter and Quantum Technologies, University of Stuttgart — 4DESY, Hamburg — 5Max Planck Institute for Intelligent Systems, Stuttgart

Glasses are indispensable in everyday life and technology. However, the microscopic mechanisms generating this state of matter remain subject to debate. Within MD simulations and the original statistical-thermodynamic ring approximation, we revealed that at the vitrification the 4-point positional correlations caused by the configurational entropy create an instability with respect to formation of a structural state with angular order. This state is described in terms of only one dominant orientational mode in the angular statistical variance of the density fluctuations, which results in a mesoscopic-scale mutual ordering of the polytetrahedral clusters. Their lifetime exhibits the well-known slowdown at approaching the glass transition point. Our results can be tested by coherent diffraction experiments at the newly developed light sources and will be an essential guide to determine the best conditions for successful experiments in a broad range of glassy systems, e.g. colloidal, metallic glasses and water.

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