A FIELD-THEORY STUDY OF THE EFFECT OF SPECIFIC INTERACTIONS IN IONIC SYSTEMS - A SIMPLE-MODEL

The effect of specific ionic interactions on the Debye length has been studied using a simple model Hamiltonian for a binary mixture of anio ns and cations in the framework of the field theory. The Hamiltonian c ontains the Coulombic interaction and an independent non-Coulombic par t describing a binary mixture of equivalent uncharged particles. We us e a local and quadratic approximation to calculate the partition funct ion via a functional integral. The Debye limiting law is obtained with a renormalized screening length. The screening is enhanced when the s pecific interactions favor demixion. This is illustrated on the exampl e of an asymmetric hard sphere mixture. (C) 1998 American Institute of Physics. [S0021-9606(98)51320-7].