Higher-order structure and statistical properties of dipolar nano-particles

Dipolar particles system has long-range interaction including the direction dependences. We calculated these systems using coarse-grained MD simulation for nano-particle systems, which have dipolar Hamiltonian and Lennard-Jones Potential at the viewpoint of self-organized nano-structure. As first order structure, we can see chain type structures. And as higher-order structure, we can see bundle and droplet condensed structures by long calculations. We can see droplet structure for small dipolar system (S=1), and bundle structure for large dipolar system (S=3). Next we calculated the specific heat by annealing simulation for dipolar particles system on soft spheres and on hard spheres. We can see the double peak for both systems. Soft sphere system has peaks at higher temperature than hard sphere system. The peak of lower temperature will be regard as solid-liquid phase transition, and the other peak will be regard as liquid-gas transition.