Abstract. In this letter, we study the ground state of two spherical macroions of identical radius, but asymmetric bare charge (Q_A > Q_B). Electroneutrality of the system is ensured by the presence of the surrounding divalent counterions. Using Molecular Dynamics simulations within the framework of the primitive model, we show that the ground state of such a system consists of an overcharged and an undercharged colloid. For a given macroion separation the stability of these ionized-like states is a function of the difference (√N_A − √N_B) of neutralizing counterions N_A and N_B. Furthermore the degree of ionization, or equivalently, the degree of overcharging, is also governed by the distance separation of the macroions. The natural analogy with ionic bonding is briefly discussed.

PACS numbers: 82.70.Dd, 61.20.Qg, 41.20.-q

Print publication: Issue 4 (15 August 2000)
Received 4 April 2000, in final form and accepted for publication 22 June 2000