ICAMS / Interdisciplinary Centre for Advanced Materials Simulation

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Heterogeneous dynamics of a simple glass under shear

Date: 25.11.2008
Place: UCGP2008 - Unifying Concepts in Glass Physics IV, Kyoto, Japan

Ingo Steinbach
Fathollah Varnik

Dynamics of a simple glass forming model (the so-called Kob-Andersen binary Lennard-Jones mixture, [W. Kob and H.C. Andersen, PRL 73, 1376 (1994)]) undergoing shear flow is studied via large scale molecular dynamics simulations. The focus of the present study is on the possibility of qualitatively different dynamic behavior at different length scales, as sometimes addressed within the concept of dynamic heterogeneity. In order to make a link between this issue and the system’s response to an external perturbation, the rather simple case of a homogeneous shear is investigated. In our simulations, a certain decoupling is observed between the dynamics at large and small length scales at temperatures close to the mode coupling critical temperature of the model [F. Varnik and O. Henrich, Phys. Rev. B 73, 174209 (2006)]. This decoupling is also manifest in a violation of the Stokes-Einstein (SE) relation (which states that the shear viscosity is inversely proportional to the diffusion coefficient of the system). Interestingly, when shear completely determines the dynamics of structural relaxation, SE-relation seems to be restored [F. Varnik, AIP CP 982, 160 (2008)].

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