ISOTHERMS OF IONIC ADSORPTION AT METAL-ELECTRODES WITH COVERAGE-DEPENDENT LATERAL INTERACTIONS DUE TO MUTUAL DEPOLARIZATION

Isotherms are calculated for a simple modal describing ions absorbing onto a metal electrode, taking into account the effect of mutual depol arization. By mutual depolarization is meant the progressive discharge of the ions with increasing coverage, leading to weaker dipole-dipole lateral interactions. The mean-field isotherm predicts sigmoidal part s in the isotherm in the region of ionic discharge, which may even dev elop into hysteresis and first-order phase transitions. The qualitativ e predictions of the mean-field theory, in particular the first-order phase transition, are reproduced by Monte-Carlo simulations, but only if the lateral repulsive interactions are long ranged, as is expected for electrostatic interactions. (C) 1998 Elsevier Science B.V.