Stick boundary conditions and rotational velocity auto-correlation functions for colloidal particles in a coarse-grained representation of the solvent

TL;DR

This paper demonstrates how to implement stick boundary conditions in a coarse-grained solvent model to accurately simulate and analyze the rotational dynamics of colloidal particles, with results matching theoretical predictions.

Contribution

It introduces a method to impose stick boundary conditions in stochastic rotation dynamics, enabling direct simulation of colloidal rotational velocity auto-correlation functions.

Findings

Quantitative agreement with Enskog theory at short times

Agreement with hydrodynamic mode-coupling theory at longer times

Enskog contribution dominates for colloids smaller than 35nm

Abstract

We show how to implement stick boundary conditions for a spherical colloid in a solvent that is coarse-grained by the method of stochastic rotation dynamics. This allows us to measure colloidal rotational velocity auto-correlation functions by direct computer simulation. We find quantitative agreement with Enskog theory for short times and with hydrodynamic mode-coupling theory for longer times. For aqueous colloidal suspensions, the Enskog contribution to the rotational friction is larger than the hydrodynamic one when the colloidal radius drops below 35nm.