Dresden 2009 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 9: Glass II

DF 9.3: Talk

Tuesday, March 24, 2009, 14:40–15:00, WIL B321

How important are facilitation processes for the dynamics in supercooled liquids? — •Christian Rehwald and Andreas Heuer — Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, 48149 Münster

We investigate a binary mixture Lennard-Jones liquid by molecular dynamics simulation with respect to finite size effects. Our focus is the q-dependent relaxation time τ(q) and the diffusion constant D calculated from particle coordinates, inherent structures and metabasins [1]. It turns out that globally defined metabasins are no longer sufficient to predict S(q,t) for large systems (except for small q). In order to avoid this problem, we calculate local exchange time distributions, generated by averaged particle displacements [2]. The locally defined distributions show a similar behavior as that of metabasins for long waiting times without depending explicitly on N. Moreover, as a result of facilitation processes, increasing the system size leads to a reduction of the long tails of the exchange time distribution. This N-dependence is exactly the one expected from a model glass-former based on a set of coupled elementary unit systems [3], which is e.g. implemented in several facilitated spin models.

[1] A. Heuer, Phys.: Cond. Mat. 20 (2008)

[2] L. O. Hedges et al., J. Chem. Phys. 127 (2007)

[3] M. Vogel et al., J. Chem. Phys. 120 (2004)