Dresden 2003 – wissenschaftliches Programm
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DF: Dielektrische Festkörper
DF 4: Gl
äser Ib (gemeinsam FV DF/DY)
DF 4.2: Vortrag
Dienstag, 25. März 2003, 10:30–10:45, HSZ/403
Higher organized dynamical cooperativity in the glass-transition regime: computer modelling for Ni0.5Zr0.5. — •H. Teichler — Institut für Materialphysik, Univ. Göttingen, and SFB 602
Understanding of the mechanisms of structural dynamics in glasses and undercooled melts is a key issue for understanding the liquid-to-glass transition as a kinetic process. For metallic glasses it seems well settled that in the melt, when approaching the critical temperature TC from above, the viscous-flow like independent particle motion gradually is suppressed in favour of a coherent motion of chains or groups of atoms through a more rigid environment. Much less is known well below TC. With regard to this, we have carried out molecular dynamics simulations for a binary Ni0.5Zr0.5 alloy model at a nominal temperature of 700 K over a time window of 2.5 µ s and at higher temperatures. The data indicate that atom chain motions become ineffective for long range matter transport in the region around the experimental glass transition temperature. Here a new type of higher organized dynamical cooperativity takes over. It is characterized by avalanches of mutually triggered transitions of chains of atoms separated by times of dynamical calmness. This transports the dynamics to a new time scale and to a new scale in space. In the light of this observation the glass transition process is addressed as well as further phenomena such as the kinetics of ageing in glassy systems, mechanical loss spectroscopy, or particle diffusion in the vitreous state.