A versatile simulation method for studying phase behavior and dynamics in colloidal rod and rod-polymer suspensions

Abstract

Here, we present an implicit-solvent model for dynamic simulations of hard-rod and rod-polymer suspensions. Individual rods are represented by a rigid linear chain consisting of overlapping spheres which interact through a pseudohard-core potential based on the cut-and-shifted Mie (generalized Lennard-Jones) potential with exponents (50, 49). In the rod-polymer suspensions, the polymers are modeled as freely interpenetrable spheres with respect to each other, while there is the pseudohard-core repulsion between the polymer and rod spheres. Dynamic simulations with this model are carried out with a dissipative particle dynamics (DPD) thermostat - each sphere is put in a larger DPD sphere and thus interacts with others via additional pairwise frictional and random forces - which captures the effects of Brownian forces due to the solvent while conserving local momentum. The phase behavior of these models, obtained from continuous compression and expansion simulations, reproduces previous predictions based on theoretical calculations and Monte Carlo simulations. Our method is suited to study dynamic processes in these suspensions, including nucleation and self-assembly, and can be readily extended to colloidal particles of different shapes and chemistry.