Journal of Colloid and Interface Science, Vol.225, No.2, 299-306, 2000
Potential distribution and electrostatic forces in wedge-shaped geometries: Analytical and numerical results
The interparticle force due to electrostatic/ionic origin in thermal equilibrium is modeled for two particles in close contact in an ion-laden fluid. The space between the particles presents approximately a wedge-shaped geometry. 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 Carlo simulation. The analytical solution is obtained by traditional means, improving the double-layer solutions for single surfaces to fit the appropriate boundary conditions (constant potential or constant charge). Arbitrary curved surfaces can be treated with the same procedure. To investigate the physical effects not accounted for by the DH field theory (for instance, the finite ion size), canonical ensemble Monte Carlo simulations of a primitive electrolyte solution in a wedge-shaped geometry have been carried out, using the Metropolis method. For regions far removed from the top of the wedge, the two methods give the same answer; however, the contribution to the force of the ionic distribution close to the apex of the wedge is non-negligible, increasingly so for smaller angles. Full results are reported.