(Color online) The radial densities obtained by MC simulations of the three species of counterions in Group 3: (z1, z2, z3) = (+1, +2, +3), (R1, R2, R3) = (2.0, 3.0, 4.0) in Å, and α+1 : α+2 : α+3 = 2.7 : 1.6 : 1. All three species have the same number of ions. This number is 100 in (a), 50 in (b), and 25 in (c), respectively. Hence the constant surface charge density decreases from (a) to (b) and to (c).