Percolation in colloidal systems with competing interactions: the role of long-range repulsion

Percolation in suspensions driven only by short-ranged attractions has been studied for a long-time due to its imminent relation with equilibrium and non-equilibrium processes, such as gelation and glass transition. Recently, the effects of an additional long-range repulsion have received attention as the competition between both contributions of the potential features are shown to be important to understand the phase behavior of many charged colloidal systems, such as proteins in aqueous solutions. Due to the inherent importance of the percolation in determining the structure of a fluid and its pertinent relation with dynamical arrest, here, we use Monte Carlo computer simulations to systematically study the influence of the repulsion on the percolation. The formation and geometry of clusters when a system percolates are investigated. Our results indicate that the addition of the long-ranged repulsion increases the average cluster size, resulting in the shift of the percolation threshold to lower volume fractions. We also show that the structure of small clusters is mostly affected by the attraction, while the morphology of intermediate and large size clusters is determined by the energetic balance between attraction and repulsion.