Application of the Dissipative Particle Dynamics Method to Ferromagnetic Colloidal Dispersions

We have investigated the validity of the application of the dissipative particle dynamics (DPD) method to ferromagnetic colloidal dispersions by conducting DPD simulations for a two-dimensional system. Firstly, the interaction between dissipative and magnetic particles has been idealized as some model potentials, and DPD simulations have been carried out using such model potentials for a two magnetic particle system. In these simulations, we have concentrated our attention on the collision time for the two particles approaching each other and touching from an initially separated position, and such collision time has been evaluated for various cases of the mass and diameter of dissipative particles and the model parameters, which are included in defining the equation of motion of dissipative particles. Next, we have treated a multi-particle system of magnetic particles, and have evaluated particle aggregates and the pair correlation function along an applied magnetic field direction. Such characteristics of aggregate structures have been compared with the results of Monte Carlo and Brownian dynamics simulations in order to clarify the validity of the application of the DPD method to particle dispersion systems. The present simulation results have clearly shown that DPD simulations with the model interaction potential presented here give rise to physically reasonable aggregate structures under circumstances of strong magnetic particle-particle interactions as well as a strong external magnetic field, since these aggregate structures are in good agreement with those of Monte Carlo and Brownian dynamics simulations.