Abstract
We investigate the clustering and phase separation of a model of ultrasoft, oppositely charged macroions by a combination of Monte Carlo and Molecular Dynamics simulations. Static and dynamic diagnostics, including the dielectric permittivity and the electric conductivity of the model, show that ion pairing induces a sharp conductor-insulator transition at low temperatures and densities, which impacts the separation into dilute and concentrated phases below a critical temperature. Preliminary evidence is presented for a possible tricritical nature of the phase diagram of the model.