ON STATISTICAL THERMODYNAMICS OF THE IDEAL POLARIZABLE INTERFACE

The fundamentals of the statistical mechanical theory of the electric double layer are discussed in relation to the choice of the independen t electric variable. It is shown that the grand canonical ensemble the ory implies the use of the potential as the independent electric varia ble. The notion of a constant charge ensemble is then introduced as a particular case of the grand canonical ensemble. The differential capa city is expressed unambiguously by charge fluctuation in the grand can onical ensemble theory, while the analogous formula in the constant ch arge ensemble theory can be interpreted as a surface excess of polariz ability, which cannot be resolved unambiguously into absolute quantiti es: dipole moment fluctuation and thickness of the interface. The impl ication of the choice of the independent electric variable for the so- called polarization catastrophe is discussed.