Phase separation in suspensions of repelling charged colloids

We use the simplest possible density functional theory to show that the purely repulsive screened-Coulomb (or DLVO) interaction between charged colloidal particles is compatible with gas-liquid, gas-solid and solid-solid coexistence in colloidal suspensions of low ionic strength of about 10 −6 moll −1 . The cohesive energy of the condensed phase, which produces a Van der Waals loop in the total free energy, is shown to be provided by the attractions between each colloidal particle and “its own” cloud of counterions. This finding may (partially) resolve the ongoing debate on attractions between like-charged particles.