Ground state of two unlike charged colloids: An analogy with ionic bonding

In this letter, we study the ground state of two spherical macroions of ide ntical radius, but asymmetric bare charge (Q(A) > Q(B)) Electroneutrality o f the system is ensured by the presence of the surrounding divalent counter ions. Using Molecular Dynamics simulations within the framework of the prim itive model, we show that the ground state of such a system consists of an overcharged and an undercharged colloid. For a given macroion separation th e stability of these ionized-like states is a function of the difference (r oot N-A - root N-B) of neutralizing counterions Na and Ng. Furthermore the degree of ionization, or equivalently, the degree of overcharging, is also governed by the distance separation of the macroions. The natural analogy w ith ionic bonding is briefly discussed.