Development of a simple assessment method regarding the overlap of spheroidal particles and its application to Monte Carlo simulations of magnetic particle suspensions

Abstract

We have developed a simple assessment method for the overlap between spheroidal particles, which is indispensable for performing particle-based simulations of a colloidal suspension. In the present assessment method, the position giving rise to the deepest overlap point between the steric layers of two spheroidal particles is evaluated by using the inscribed sphere of the spheroid that is moved on the major axis line for scanning the surface-to-surface distance of these two spheroids in an effective manner. Moreover, we have developed an evaluation method for the interaction energy due to the overlap of the steric layers covering spheroidal particles. This is based on a sphere-connected particle model, but some modifications are introduced in order to express an appropriate repulsive interaction energy at the deepest overlapping position. Then we have investigated phase change problems in a magnetic spheroidal particle suspension in a two-dimension system by means of Monte Carlo simulations where both the above-mentioned assessment method and the evaluation method for the repulsive interaction energy are combined. In the case of no external magnetic field, as the area fraction is decreased from a large value where chcain-like clusters are formed in the whole area of the system, this internal strucuture changes into raft-like one in a narrow range of the area fraction. Raft-like clusters are preferred in a weak applied magnetic field, but an increase in the field strength induces the phase change from raft-like into chain-like structure.

Keywords

• magnetic colloidal dispersion
• magnetic rod-like particle
• magnetic spheroidal particle
• overlap assessment
• monte carlo simulation
• surface modification
• phase change