SIMULATION OF CONFINED PRIMITIVE ELECTROLYTES - APPLICATION OF A NEW METHOD OF SUMMING THE COULOMB FIELD

Recently, Lekner has presented a new method to sum the Coulomb forces between charged particles of a central system and its images extended periodically in 2- and 3- dimensions. In this paper we apply the new method in canonical ensemble Monte Carlo (CMC) simulations of the primitive electrolyte confined between two planar surfaces: one is charged and the other is neutral. The anions and cations have identical size with diameter d = 4.25 angstrom and interact with a hard sphere repulsion and Coulomb interaction. In Lekner's method the long range Coulomb potential is computed from a series of Bessel functions. We have demonstrated that the series converges after about 10 terms and so is computationally quite simpler than the Ewald sum methods. The method is also faster for confined electrolytes than are those Ewald-like sum methods with which we compared it. In our simulations, we obtained the density distributions and mean electrostatic potentials of the confined system for the 1 : 1 electrolyte having concentrations equal to those of 1 M and 2 M bulk electrolyte and having different surface charge densities. For large separation of confining walls, the canonical ensemble Monte Carlo results agree with previously reported grand canonical Monte Carlo results.