Simulation of dense colloids

Abstract

We present in this proceeding recent large scale simulations of dense colloids. On one hand we simulate model clay consisting of nanometric aluminum oxyde spheres in water using realistic effective electrostatic interactions and Van der Waals attractions, known as DLVO potentials and a combination of molecular dynamics (MD) and stochastic rotation dynamics (SRD). We find pronounced cluster formation and retrieve the shear softening of the viscosity in quantitative agreement with experiments. On the other hand we study the velocity probability distribution functions (PDF) of sheared hard-sphere colloids using a combination of MD with lattice Boltzmann and find strong deviations from a Maxwell-Boltzmann distribution. We find a Gaussian core and an exponential tail over more than six orders of magnitude of probability. The simulation data follow very well a simple theory. We show that the PDFs scale with shear rateγ as well as particle volume concentration φ, and kinematic viscosity ν.

Microscopic relationship between colloid–colloid interactions and the rheological behaviour of suspensions: a molecular dynamics-stochastic rotation dynamics investigation

“…This approach provides an step to improve existing phenomenological formulations. Stochastic Rotation Dynamics (SRD) has been applied successfully to account for hydrodynamic interactions, in sedimentation processes [7] or the cluster formation and the shear softening of the viscosity in a solution of Al 2 O 3 particles [8]. More recently, Laganapan et al used SRD algorithms to compute the shear viscosity of spheres at different Péclet numbers [9].…”