  Neutral grains made of the same dielectric material can attain considerable
charges due to collisions and generate long-range interactions. We perform
molecular dynamic simulations in three dimensions for a dilute, freely-cooling
granular gas of viscoelastic particles that exchange charges during collisions.
As compared to the case of clustering of viscoelastic particles solely due to
dissipation, we find that the electrostatic interactions due to collisional
charging alter the characteristic size, morphology and growth rate of the
clusters. The average cluster size grows with time as a power law, whose
exponent is relatively larger in the charged gas than the neutral case. The
growth of the average cluster size is found to be independent of the ratio of
characteristic Coulomb to thermal energy, or equivalently, of the typical
Bjerrum length. However, this ratio alters the crossover time of the growth.
Both simulations and mean-field calculations based on the Smoluchowski's
equation suggest that a suppression of particle diffusion due to the
electrostatic interactions helps in the aggregation process.
