Condensed Matter Physics, 1993, No. 2, p. 4-20, English

Authors: G.Stell

A class of statistical-mechanical model of associating atoms or ions is described. Conditions that must hold for them in the complete-association (confinement) limit are noted. In the simplest version of the models considered, this is the pure-solvent limit, of fundamental importance in solution theory. It is shown that the confinement limit is much like a critical-point limit, at which the direct correlation function assumes a, very special long-ranged form. OFf-confinement (partially-associated) states are then considered and a sequence of successively simpler approximations for the pair distribution functions are proposed on the basis of an Ornstein Zernike-type equation. Explicit expressions due to Zhou and Stell are given for the simplest of these approximations, which is relevant both when the associating atoms, are uncharged or when the fully associated system is of high dielectric constant. In the complete-association limit, these expressions apply to dipolar dumbbells with interpenetrating cores over a continuous range of interpenetration.

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