Dresden 2009 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 8: Glass I

DF 8.6: Vortrag

Dienstag, 24. März 2009, 11:40–12:00, WIL B321

Mechanisms of atom dynamics on the microseconds scale during the alpha-decay in MD simulated glass forming Ni0.5Zr0.5. — •Helmar Teichler — Institut für Materialphysik, Universität Göttingen, Göttingen, Germany

In glass forming melts near TG, the alpha-decay reflects relaxation processes on meso- and macroscopic time scales. Its microscopic explanation is a challenging open question, as it needs to understand emergence of extreme slow dynamics, more than ten orders of magnitude below atomic vibrations, from the atomic motions in the melt. Here we present molecular dynamics simulation results on the microseconds scale for glass forming Ni0.5Zr0.5 at 785 K, aimed at elucidating the microscopic processes of meso-scale dynamics during the alpha-decay well below the critical temperature Tc of mode coupling theory.- From the self intermediate scattering function we find that avalanches of collectively moving atoms, local in space and time, dominate these dynamics. The avalanches are known as higher organized cooperative processes in high-viscous dynamics [H. Teichler, PRE 71, 031505 (2005); JNCS 312, 533 (2002)], and more recently as "democratic particle motion" [G.A. Appignanesi et al. PRL 96, 057801 (2006)]. From our MD data, avalanches turn out as rare events, being created at or near a preceding one with about microsecond delay. Our results are discussed with regard to the dynamical facilitation model of Garrahan and Chandler.