Project A5

Computer Simulations of Structure, Dynamics, and Phase Behavior of Colloidal Fluids in Confined Geometry and Under Shear

Project leaders

Summary

Two types of colloidal systems exposed to shear deformation will be studied, a model for colloid-polymer mixtures under confinement, and a glass-forming binary soft sphere mixture. Polymers are described as soft spheres weakly interacting with each other, while colloid-polymer and colloid-colloid pairs interact with the (repulsive) Weeks- Chandler-Andersen potential, so that a depletion attraction between colloids results, similar to the Asakura-Oosawa model. Confining this system between parallel plates, the interplay between phase separation and shear will be studied by Non-Equilibrium Molecular Dynamics, including the suppression of capillary waves at confined interfaces by the shear. Confinement in cylindrical geometry will also be considered. The glass forming mixture is described by particles interacting with Yukawa potentials, and shear is implemented via Lees-Edwards boundary conditions. The study of transient time-dependent phenomena will be extended to systems under oscillatory shear and to systems that are subject to a constant shear stress. The latter problem is the macrorheological counterpart to the micro-rheological simulation of a pulled probe particle, thus enabling to elucidate the relation between micro- and macro-rheology. The results of the simulation will be compared to those from mode-coupling theory and experiment.