Studies on charge interaction dynamics between interfaces

Abstract

The counterion density profile and pressure between two inhomogenously charged parallel plates are analyzed analytically and numerically in the strong-coupling regime. Point charges are used and the surface charges are immobile. It is found that when the surface charge distribution is inhomogeneous, the charge coupling effect becomes stronger, the counterion spatial distribution is more localized toward the plate surfaces and, thus, the pressure between two plates becomes lower than the case when the surface charge distribution is homogeneous. It is also found that the pressure is not only function of the phase in surface charge inhomogeneity, but also function of many other parameters such as plate-toplate distance and counterion charge valence relative to the surface anion charge. At higher counterion valence, the surface charge inhomogeneity effect gets weaker. The counterions are strongly interact with surface ion if surface charge is discrete and mobile. As a result higher association observed than immobile surface ions. The strong localization phenomena are common regardless of valence. But the behavior of strong attraction between surface ions and counterions is differ as the valence of counterions. When the valence is 2, counterions binding two surface ions. The pressure between two charged surface becomes less attractive as compared to in phase case of immobile surface charges. When the valence is 1, counterions and surface ion make pair and the system is analyzed by dipole interaction. There is no repulsive hill when it is allowed the surface charge to move. Especially for mono valence case, the dipole fluctuation induced attraction decays very fast. The dielectric difference plays a crucial role in charged system. When the dielectric constant of inside slab is greater than that of outside slab, the same sign image charge is generated and as a result counterions are driven to plates. Besides When the dielectric constant of inside slab is smaller than ...