A rapidly convergent series for calculation of the interaction between two similar plane double layers for Na2SO4 type asymmetric electrolytes at positive surface potential

Vz−z′ and V′ in the figure are the interaction energies of symmetric and Na2SO4 type asymmetric electrolytes at y>0, respectively. Vz−z′ must intersect V′ at a certain ξd. When ξd is smaller, V′>Vz−z′; when ξd is larger, V′