ACCURATE ANALYTIC FORMULAS FOR THE DOUBLE-LAYER INTERACTION BETWEEN SPHERES

Very simple but accurate analytic formulas are presented for the electrical double-layer force and interaction free energy between two spherical colloidal particles, valid up to the moderate to high-potential regime. These formulas represent a remarkable improvement on previous analytic and semianalytic formulas for the interaction, while maintaining an excellent degree of analytic simplicity. Furthermore, a detailed derivation of the interaction free energy between two dissimilar spheres in the linear Debye-Huckel approximation is presented that is valid for all kappa h, where kappa is the Debye screening parameter and h is the distance of closest approach between the spheres. In doing so, it is demonstrated that the well-known Hogg-Healy-Fuersteneau (HHF) formula, which is valid only in the small Kh regime, may be trivially modified to extend its range of applicability to all Kh. (C) 1995 Academic Press, Inc.