ELECTROSTATIC INTERACTION BETWEEN 2 DISSIMILAR SPHERES - AN EXPLICIT ANALYTIC-EXPRESSION

Explicit exact analytic expressions are obtained in the form of infinite series for the potential distribution and the potential energy of the electrostatic interaction for the system of two dissimilar hard spheres at constant surface potentials in an electrolyte solution on the basis of the linearized Poisson-Boltzmann equation. The leading term of the expression for the interaction energy (the zeroth-order approximation) corresponds to the interaction energy that would be obtained if both spheres were ion-penetrable particles (“soft” particles) and to that obtained by the linear superposition approximation. The first-order approximation corresponds to the interaction energy that would be obtained if either sphere were a soft particle (the other being hard). The first-order correction term consists of two subterms, each of which depends only on the surface potential of the soft sphere, and can be interpreted as the attractive interaction between the soft sphere and its image with respect to the hard sphere. © 1994 Academic Press, Inc.