Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 16: SYMPOSIUM Driven Soft Matter I
CPP 16.6: Vortrag
Dienstag, 26. Februar 2008, 11:45–12:00, C 130
Diffusion and Taylor dispersion in a simple glass under shear — •Fathollah Varnik — Max-Planck Institut für Eisenforschung, Düsseldorf, Germany
We investigate, via MD simulations of a simple glass, large scale dynamics under homogeneous shear by evaluating the time dependence of the mean square displacements for temperatures ranging from the supercooled state to far below the mode coupling critical temperature of the model. Particularly long simulations are performed allowing an accurate determination of the diffusion constant. For low temperatures and at not too high shear rates, the mean square displacements exhibit the well known two step relaxation behavior with a long time diffusive motion along the spatial directions perpendicular to the flow. In the flow direction, on the other hand, a third regime follows the diffusive motion, where Taylor dispersion with the typical t3 time dependence clearly dominates the long time behavior of the particle displacements. Once this contribution is subtracted, normal diffusive behavior is recovered in the limit of long times. Comparing diffusive motion along the flow, the shear gradient and the vorticity (neutral) directions reveals small but systematic anisotropy in particle dynamics.