Two-Dimensional Self-Assembly of Similarly Charged Granular Particles

We present results of our experimental study on the effect of particle surface coverage (density) on the evolution of packing structure in charged granular assemblies in a two-dimensional (2D) geometry. Steel particles were charged by rubbing them with the bottom surface of a polystyrene box. We conducted a Monte Carlo simulation study via the interparticle interaction of the dipole repulsion. The resulting radial distribution functions, bond orientation correlation functions, and 2D pressure isotherm approximate the experimental data well. The particle potential of the mean force changes from repulsion only at a low particle coverage fraction of 0.01 to oscillation between repulsion and attraction at higher coverage fractions due to the collective particle interactions.