Dresden 2017 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 37: Fluids and Glasses I

CPP 37.2: Vortrag

Mittwoch, 22. März 2017, 10:30–10:45, ZEU 255

Metabasin Lifetimes of Sheared Supercooled Liquids — •Markus Blank-Burian and Andreas Heuer — Institut für Physikalische Chemie, WWU Münster, Deutschland

In the limit of small shear rates and temperatures around the glass transition temperature Tg, a sheared supercooled liquid can be described by hopping processes between so called metabasins [1]. However, in the limit of small temperatures and high shear rates the dynamics can be described by vanishing energy barriers in the PEL [2].

We analysed this crossover region with molecular dynamics simulations at various temperatures (0.01 ≤ T ≤ 1.0) and shear rates (10−6 ≤ γ ≤ 10−1). A very small system size (N = 130) was used, which is not affected by major finite size effects. A plastic event in this system size typically spans the whole box, so that the system does not show shear banding.

We can show, that two simple models, describing the metabasin lifetimes under constant shear rate and finite temperature, are in good agreement with our numerical data. The first model assumes that the metabasin energy dependent activation barriers are continuously reduced by shearing the system. The second, more simplistic model, assumes a superposition of transition rates, reflecting the limit of low temperature and the limit of low shear rates, respectively, to characterize the transition region between temperature- and shear-dominated dynamics.

[1] A. Heuer, J. Phys.: Condens. Matter 20, 37 (2008)

[2] D. J. Lacks, Phys. Rev. E 66, 5 (2002)

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