Limitations of Multistate Solvent Models at an Electrode/Electrolyte Interface: A Numerical Study Using the Bethe Approximation

Abstract

The consequences of employing the Bethe approximation for dipolar interactions in the inner part of the electrical double layer are examined. Apart from providing explicit results for order parameters, dipolar potential, and differential capacitance for a two-state polarizable point dipole model, a nonlinear regression analysis using experimental data is carried out in order to estimate interfacial constants such as permanent dipole moment, polarizability, effective coordination number, etc. This indicates that the simultaneous agreement of dipole potential and differential capacitance variations with charge density on the metal surface cannot be obtained using conventional discrete multistate orientational state models, thereby pointing to the need for explicit introduction of a metal surface into the double layer theories.