Controlling the percolation threshold of conductor-insulator composites by changing the granular size of insulators

When one attempts to modulate and control the characteristics of composite materials, limit of the modulation may be dictated by the mathematical threshold of the percolation transition. We report our computer simulation, in which percolation behavior can strongly be controlled by introducing size differences in the insulator particles rather man the conductor particles. This modulation effectively lowers the transition point to 0.52, from about 0.59 achieved with the conventional 2D site percolation model. Although a similar effect has already been reported for off-lattice systems and experiments, this is the first observation and analysis made in a basic 2D lattice model. Also, we show that this effect of threshold reduction is also related to the shape difference of the insulator particles. Such an observation in a basic model is believed to be fundamental to exploiting this phenomenon in real applications.