Distribution of counterions and interaction between two similarly charged dielectric slabs: Roles of charge discreteness and dielectric inhomogeneity

Abstract

The distribution of counterions and the electrostatic interaction between two similarly charged dielectric slabs is studied in the strong coupling limit. Dielectric inhomogeneities and discreteness of charge on the slabs have been taken into account. It is found that the amount of dielectric constant difference between the slabs and the environment, and the discreteness of charge on the slabs have opposing effects on the equilibrium distribution of the counterions. At small inter-slab separations, increasing the amount of dielectric constant difference increases the tendency of the counterions toward the middle of the intersurface space between the slabs and the discreteness of charge pushes them to the surfaces of the slabs. In the limit of point charges, independent of the strength of dielectric inhomogeneity, counterions distribute near the surfaces of the slabs. The interaction between the slabs is attractive at low temperatures and its strength increases with the dielectric constant difference. At room temperature, the slabs may completely attract each other, reach to an equilibrium separation or have two equilibrium separations with a barrier in between, depending on the system parameters.

Fractionation of cellulose nanocrystals: enhancing liquid crystal ordering without promoting gelation

“…According to Pezeshkian et al 39 , the repulsion at close distances disappears with increasing charge discreteness, and at low temperatures, the plates always attract each other. This effect also contributes to the attraction of the rod ends.…”

“…One also notes that the electrostatic interaction between charged surfaces at close distances has recently been considered beyond the DLVO theory for both uniform and discrete surface charge distributions [39][40][41][42] . According to Pezeshkian et al 39 , the repulsion at close distances disappears with increasing charge discreteness, and at low temperatures, the plates always attract each other.…”

Image-charge forces in thin interlayers due to surface charges in electrolyte

“…(20) was derived under the condition κ 1/h; therefore, its applicability to films with a thickness of several monolayers (i.e., on the order of 1 nm) is justified for solutions of symmetric 1-1 electrolyte with concentration greater than 1M. Such solutions can be treated in the frame of the Debye-Hückel approximation for the case of insignificant ion-ion correlations only.…”

“…This deviation is most noticeable at the scale of several atomic distances around the charge location. As shown in numerous papers [12,13,18,[20][21][22][23], charge discreteness affects the electric potential distribution in the vicinity of interfaces, diffusion and overcharging processes at the interfaces, the disjoining pressure in liquid interlayers, and the aggregation kinetics in dispersions.…”

“…Extensive studies in this area have been conducted for decades [1][2][3][4][5][6][7]. The focus in the theoretical studies of recent decades was on the systems important for colloid physics, biophysics, or biochemistry, in which the charges are located either in the vicinity of a single interface between bulk electrolyte and dielectric phases, or in the nanosize films of electrolytes, or, finally, in the dielectric interlayers confined (at least on one boundary) by an electrolyte solution [8][9][10][11][12][13][14][15][16][17][18][19][20].…”