A novel method of calculating the interaction energies of double layers

A novel, simple, and efficient method to calculate the interaction energies of double layers, lambda parameter method, is presented by introducing a parameter lambda in the elliptical integral. The interaction energies between two similar plane parallel double layers are expanded in the power series with such a method. The series converge very fast. When the dimensionless surface potential of double layers is less than or equal to 30, the number of the series terms required does not exceed 3 to obtain the interaction energies with six significant digits.