Two rapidly convergent series for calculating the interaction energies between two dissimilar double layers for Na2SO4 or CaCl2 types asymmetric electrolytes at y0 > 0 > yd ≥ ?y0

Two rapidly convergent series for calculating the interaction energies between two dissimilar double layers for Na₂SO₄ or CaCl₂ types asymmetric electrolytes at y ₀ > 0 > yd ≥ −y ₀ were derived, the number of the series terms required to obtain the interaction energies with six significant digits is not more than 4 when the dimensionless surface potential of two dissimilar double layers changes from −20 to + 20. The absolute values of the interaction energies V between two dissimilar double layers for Na₂SO₄, CaCl₂ and NaCl types electrolytes obey the following relations: when −y _d = y ₀, V′Na₂SO₄ = V′CaCl₂; when −y _d > y ₀, V′Na₂SO₄ > V′CaCl₂; when −y _d < y ₀, V′Na₂SO₄ < V′CaCl₂; V′Na₂SO₄ or V′CaCl₂ is always less than V′_NaCl. Several approximate expressions were given for interaction energy at y ₀ and −y _d ≪ 1.