Modeling the structural and transport behavior of hard ellipsoidal colloids using event-driven Brownian dynamics

Abstract

The theory for hard spheres is well established and has provided notable contributions in the field of colloid science. However, real systems are usually composed of anisotropic particles and there is significantly less theoretical information available for such systems. Hard ellipsoids can serve as natural extensions of the hard-sphere model. While the deviation from the hard-sphere geometry is small, it can already exhibit a wide range of new properties, such as liquid crystalline order, that one can explore. In this work, we study the dynamics of a system of colloidal hard ellipsoids in the context of glass transition using an event-driven Brownian dynamics model. The main challenge is to ensure that the detection of collisions and the sampling of random displacements do not produce overlaps. To this end, we develop an algorithm following the models proposed by Donev (2005) and De Michele (2007), where an overlap-potential that depends on the relative translation and rotation of a pair of ellipsoids, can be defined and used to predict the next collision time. To benchmark the model, transport properties such as the mean squared displacements and mean squared angular displacements are calculated and compared with experimental hard ellipsoidal colloids. By benchmarking the single particle motion, the structural and transport properties can be used to gain insight into dense dispersions of anisotropic colloids.