Structural transition of various-sized sphere-platelet mixtures.

Monte Carlo simulations on the structural change of hard sphere-platelet mixtures were performed to investigate the effect of particle size. We quantitatively analyzed local equilibrium structures of sphere-platelet mixtures with varying size ratios under various sphere and platelet density conditions. Based on the simulation results, we investigated the structural transitions such as isotropic to anisotropic, clustering, and so on. When a small amount of small-sized sphere is added to a large-sized platelet system, the mixture structure transitions from isotropic to nematic ones as the platelet number density increases. On the other hand, the platelet forms clusters with the addition of a large number of spheres. In a small platelet-large sphere system, the spheres form aggregates by increasing platelet density instead. The platelet and spherical particles exhibit different structural transitions depending on the size and density. In the limit of small and large size ratios, the structures of the platelet-sphere mixture obtained from the Monte Carlo simulation are close to those shown by previous theoretical and experimental studies, respectively. Because the primary actor shifts from sphere to platelet as the size ratio changes, the transition boundary shifts continuously. When the size ratio is close to unity, the most complicated behavior is observed, with both the platelet and sphere simultaneously acting the leading part.