Screening of ion-ion correlations in electrolyte solutions adsorbed in electroneutral disordered matrices of charged particles: Application of replica Ornstein-Zernike equations

The replica Ornstein-Zernike (ROZ) equations for an ionic fluid adsorbed in an electroneutral, disordered matrix of ions were applied to a model where both ionic subsystems were presented as point charges interacting only via Coulomb forces. The effects of fluid (electrolyte) and matrix concentration on the screening of the ion-ion interactions in the fluid phase were investigated. The effects of the prequenching conditions were also examined. It was shown that augmenting the matrix concentration promotes attraction between equally charged ions and repulsion between ions of opposite sign. This peculiar behavior, observed first in the simulation study of Bratko and Chakraborty [J. Chem. Phys. 104, 7700 (1996)], follows straightforwardly from the ROZ equations. Moreover, we generalized the expression for the disorder averaged ion-ion potential for an arbitrary fluid concentration and prequenching conditions. In addition to these results, which are consistent with computer studies, we present some new results that have not been observed in simulations. For example, alternating ionic ordering, generated by the influence of the charged matrix was observed. This contribution can be considered as a first step toward a study of primitive model electrolytes adsorbed in disordered matrices of hard-sphere ions. The solution of this problem will be presented elsewhere. (C) 1997 American Institute of Physics.