ELECTROSTATIC INTERACTIONS BETWEEN 2 SPHERES - SOLUTIONS OF THE DEBYE-HUCKEL EQUATION WITH A CHARGE REGULATION BOUNDARY-CONDITION

The electrostatic interaction between a pair of spherical colloidal particles is analyzed using a charge regulation model to span behavior ranging from constant potential to constant charge boundary conditions. Electrostatic interparticle forces are calculated through a multipole expansion, the linear superposition approximation, and, for strongly overlapping thin double layers, the "Derjaguin approximation." By comparing the forces calculated via the different methods, we establish the range of surface parameters for which the Derjaguin approximation and linear superposition are valid in a manner similar to that employed by A. B. Glendinning and W. B. Russel (J. Colloid Interface Sci. 93, 95 (1983)). It is shown that the Derjaguin approximation furnishes an accurate representation over a wide range of surface conditions for the charge regulation model. © 1992.