MOLECULAR-SOLVENT MODEL FOR AN ELECTRICAL DOUBLE-LAYER - EFFECTS OF IONIC POLARIZABILITY

The effect of ionic polarizability on properties of the electrical dou ble layer is considered by extending a theory of Kusalik and Patey [J. Chem. Phys. 92, 1345 (1990)] to the case of an ion at a distance r fr om a charged macroion. The reference hypernetted-chain theory is solve d for a fully molecular model of the double layer and the results are compared with previous results for an identical model without polariza bility and with experimental data for double layers in alkali halide s olutions. Polarizability is found to have a large effect on the differ ential capacitance at high surface charges and to make a substantial c ontribution to the experimentally observed asymmetry in this quantity. This effect is shown to have its origin, not in any structural change in the double layer, but in the contribution to the potential from th e induced polarization of the ions themselves.