APPROXIMATE EXPRESSIONS FOR INTERACTION OF TWO SIMILAR PLANE PARALLEL DOUBLE LAYERS AT ARBITRARY POTENTIAL
Two approximate expressions used to compute the interaction energy between two similar plane parallel double layers are derived by expanding the interaction energy in the power series of [Formula: see text] at low dimensionless surface potential y0 or the power series of [Formula: see text] at high dimensionless surface potential y0, respectively. Two series converge very fast. In the range of dimensionless surface potential of colloid particles y0 from 1.00000×10-1 to 3.00000×10, when C<-4.30000, the high potential expression is usable; when C≥-4.30000, the low potential expression is usable. The required series terms will not exceed four to obtain the interaction energy with six significant figures if a low potential expression and a high potential expression are combined.