Two-dimensional structure of dipolar heterogeneous dumbbells

Abstract

The influence of polarization on the two-dimensional structure of heterogeneous dumbbells is studied by Monte Carlo simulation. The dumbbell consists of two fused hard spheres whose centers are embedded with point dipoles and , respectively. The axis of the dumbbell can rotate freely in the x-y plane but and are always along the x-axis which is the polarization direction. When the dipolar strength μa is much larger than μb, the dumbbells are perpendicular to the polarization direction and form zigzag chains; when μa and μb are comparable, the dumbbells will form end-to-end chains if and are parallel, or side-by-side chains if and are antiparallel. All the chains are along the polarization direction and the detailed information about them is given through extracting the radial and angular distributions from the simulation results. Finally, we calculate the energies of four kinds of ideal chains to explain structural transition. Our simulation results can explain the very recent experiment by Nagao D. et al. (Langmuir, 28 (2012) 6546) which studied the assembly of dumbbells with inducible dipoles, where magnitude of the dipoles was frequency-dependent and by changing frequency, different assemblies could be obtained.