Potential distribution and electrostatic forces in wedge-shaped geometries: Analytical and numerical results

The interparticle force due to electrostatic/ionic origin in thermal equili brium is modeled for two particles in close contact in an ion-laden fluid. The space between the particles presents approximately a wedge-shaped geome try. Two methods are used to ascertain the value of the interparticle force : an analytical approximation (equivalent to the traditional Debye-Huckel ( DH) method) and a simulation of the ionic fluid using a canonical Monte Car lo simulation. The analytical solution is obtained by traditional means, im proving the double-layer solutions for single surfaces to fit the appropria te boundary conditions (constant potential or constant charge). Arbitrary c urved surfaces can be treated with the same procedure. To investigate the p hysical effects not accounted for by the DH field theory (for instance, the finite ion size), canonical ensemble Monte Carlo simulations of a primitiv e electrolyte solution in a wedge-shaped geometry have been carried out, us ing the Metropolis method. For regions far removed from the top of the wedg e, the two methods give the same answer; however, the contribution to the f orce of the ionic distribution close to the apex of the wedge is non-neglig ible, increasingly so for smaller angles. Full results are reported. (C) 20 00 Academic Press.