Berlin 2005 – wissenschaftliches Programm
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DF: Dielektrische Festkörper
DF 7: Gl
äser I (gemeinsam mit FV DY)
DF 7.8: Vortrag
Montag, 7. März 2005, 12:00–12:15, TU A060
Is there a connection between microscopic particle arrangements and local heterogeneous dynamics in supercooled liquids? — •Hans König — Johannes Gutenberg-Universität Mainz, Institut für Physik, D-55099 Mainz
A binary 2D glass former of superparamagnetic colloids is experimentally investigated. The particles are confined to a plane water-air interface of hanging droplet geometry due to gravity. The particle positions are time-dependently distinguished by video-microscopy. An external magnetic field perpendicular to the monolayer allowed tuning the repulsive dipole-interaction between the induced magnetic moments from outside. The system is described by an interaction parameter Γ, given by the magnetic potential divided by kBT. Because of this ratio, Γ corresponds to an inverse system temperature.
The amorphous particle configurations are microscopically characterized by triangles of nearest neighbouring particles (TNNP). These triangles form the cages around each particle. Their stability is responsible for locally resolved heterogeneous dynamics and α-relaxations. The local packing is compared to the idealized local density optimized so-called elementary triangles (ET). Large deviations between TNNP and ET detect less densely packed regions in the monolayer. There, fast moving particles are expected. However, does local structure rules dynamics like mode coupling theory predicts?