Dresden 2014 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 4: Glasses (Joint Session with DY and CPP)

DF 4.8: Talk

Monday, March 31, 2014, 17:00–17:15, ZEU 146

Microscopic theory for sheared colloidal glasses and gels — •Christian Amann and Matthias Fuchs — Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany

We use mode coupling theory (MCT) to calculate in three dimensions (3D) transient density autocorrelators in start-up shear flow. It is thus possible to quantitatively predict flow curves and distorted structure of colloidal glasses and gels under shear flow. We investigate the transient, non-linear, non-monotonous stress response to strain and structure-factor distortion in 3D as well as steady-state flow curves (cf. [1] for 2D calculations). Density correlators, stress response, and structure-factor distortions are in good qualitative agreement with experiments [2], while the quantitative errors of the theory can be identified. A close connection between the time-evolution of symmetries of structure-factor distortions and non-monotonous stress response (i.e. stress overshoot) can be observed. We use as input a structure factor calculated with analytical Percus Yevick closure, which allows to approximate a hard sphere repulsion as well as augmenting a short range square-well attraction [3]. Hence, implications of a gel-glass to repulsive-glass transition on the transient rheology can be studied.

[1] Amann, C.P. et al. J. Rheol. 57, 149 (2013); Henrich O. et al. Phil. Trans. R. Soc. A 367, 5033 (2009)

[2] Denisov, D. et al. Sci. Rep. 3, 1631 (2013)

[3] Dawson K. et al. PRE 63, 011401 (2000)