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From equilibrium to steady state: The transient dynamics of colloidal liquids under shear

: Zausch, J.; Horbach, J.; Laurati, M.; Egelhaaf, S.; Brader, J.M.; Voigtmann, T.; Fuchs, M.


Journal of Physics. Condensed Matter 20 (2008), Nr.40, Art. 404210, 13 S.
ISSN: 0953-8984
Fraunhofer ITWM ()

We investigate stresses and particle motion during the start-up of flow in a colloidal dispersion close to arrest into a glassy state. A combination of molecular dynamics simulation, mode-coupling theory and confocal microscopy experiments is used to investigate the origins of the widely observed stress overshoot and (previously not reported) super-diffusive motion in the transient dynamics. A link between the macro-rheological stress versus strain curves and the microscopic particle motion is established. Negative correlations in the transient auto-correlation function of the potential stresses are found responsible for both phenomena, and arise even for homogeneous flows and almost Gaussian particle displacements.