On the transition from the lattice-like structure of electrolytes to the Debye–Hückel limit

Abstract

Charge densities around a central ion are calculated with the assumption of a slightly distorted normal distribution of point-charge ions around regular lattice sites. The conditions under which this charge distribution approaches that of the Debye–Hückel theory at infinite dilution are discussed. The lattice model in this form predicts oscillations in the charge cloud at any finite concentration, but these oscillations are very far from the central ion in dilute systems. Pair correlation functions are also reported for concentrated solutions. The shift of the first-neighbour maxima follows a concentration dependence steeper than the cube-root law for oppositely-charged pairs and less steep for like-charged pairs. The excess energy has been calculated and is in very good agreement with the HNC and MSA theory for low concentrations.