Monte Carlo simulation of the electric double layer: dielectric boundaries and the effects of induced charge

To model the double layer near an electrode, theories and simulations must include the different dielectric coefficients of the electrode, the commonly-postulated ‘inner’ layer, and the electrolyte. Recently, Boda et al. [D. Boda, D. Henderson, K.-Y. Chan, D.T. Wasan. Phys. Rev. E, 69, 046702, (2004)] developed a technique to include inhomogeneous dielectric coefficients in arbitrary geometries in a simulation. Here, Monte Carlo simulation results based on this method are reported for the density profiles of 1:1, 2:2 and 2:1 aqueous electrolytes. The simulations include two dielectric boundaries, one from an inner layer of low dielectric coefficient and one from an uncharged metal electrode. In addition, an extension of a Poisson–Boltzmann (PB) type theory due to Onsager and Samara [L. Onsager, N.N.T. Samara. J. chem. Phys., 2, 528, (1934)] is developed and compared with our simulation results. This approach works best for 1:1 salts at low concentrations.