Dielectric boundary effects on the interaction between planar charged surfaces with counterions only.

Using Monte Carlo simulations in conjunction with periodic Green's function methods, we study the interaction between planar charged surfaces with point-like counterions only in the presence of dielectric boundaries. Based on the calculated pressure profiles, we derive phase diagrams featuring correlation-induced negative pressure and thus attraction between the plates for large coupling parameters, i.e., low temperature or high surface charge and high ion valency. The counterion density profiles for low-dielectric and high-dielectric (metallic) surfaces are very different from the idealized case of a homogeneous dielectric constant. By contrast, the phase diagrams including the critical point and the two-phase coexistence region are rather insensitive to the presence of dielectric boundary effects. The single-image approximation that has been used in simulations before is by comparison with the exact formalism shown to be very accurate for low-dielectric surfaces but not for metallic surfaces.