Integral equations in ionic solution theory

Abstract

An exact formal integral equation is derived for the solute radial distribution functions in a multi-component solution of ions interacting with a Coulomb potential plus a short-range potential. The equation resembles, in a certain sense defined by the use of a diagram formalism, the recent exact equation of the theory of fluids but involves the Debye-Hückel potential of average force (i.e. a shielded Coulomb potential plus the short-range potential) instead of the total direct potential. Well-defined approximations yield equations which are analogues of the hypernetted chain and Percus-Yevick equations. The possible usefulness of the equations for ionic solutions and defects in ionic crystals is indicated.