ABSTRACT
In the following sections we demonstrate molecular simulations of a suspension composed of several magnetic particle models that have been explained in the preceding chapters. In the present section, we address a suspension composed of magnetic cube-like particles in thermodynamic equilibrium in order to discuss the aggregation phenomena of these particles in an external magnetic fi eld. The Monte Carlo method is employed as a simulation tool because it has a signifi cant advantage as a simulation technique for thermodynamic equilibrium in that a series of Monte Carlo simulation procedures can be conducted even if the mathematical expression for the interaction of the repulsive layer covering each particle has not been obtained. This is because in Monte Carlo simulations, a solid particle model without a repulsive layer can be used as a fi rst approximation, which yields a signifi cant advantage to Monte Carlo method. In contrast, an explicit expression of the repulsive interaction is indispensable for dynamic simulation methods such as molecular dynamics and Brownian dynamics methods. From the viewpoint of developing a technology of changing surface quality, we focus here on a two-dimensional system where cube-like particles move with their bottom plane in contact with a plane representing the material surface. The orientation and confi guration of the particles will be infl uenced by a variety of factors such as the magnetic particle-particle and particle-fi eld interactions, which are treated in the discussion of the simulation results. Qualitative discussion is made in terms of snapshots that may provide readers with a direct image of the particle aggregate formation, and quantitative discussion is made using the order parameter
and the cluster size distribution that describe the characteristics of the microstructure of the aggregates.
