ON THE ASYMPTOTIC STRUCTURE OF FAR-FIELD ELECTROSTATIC INTERACTIONS BETWEEN CHARGED MOLECULES AND CHARGED SURFACES

A general asymptotic theory is presented for approximating the electro static free energy of interaction between a charged spherical solute o f radius a and an arbitrarily shaped charged wall at distance l in the limit a much less than l. The Debye screening length is assumed to be of order l or larger. Thus, the analysis specifically addresses the m ost interesting case where strong interactions arise from the overlap of solute and wall double layers. Surface charges are represented in t erms of constant-potential boundary conditions. The asymptotic theory is shown to agree well with detailed numerical calculations for the il lustrative case of sphere-plane interaction even when the solute surfa ce is only one radius away from the wall.