Relative permittivity in stern and diffuse layers

Stern layer and outer Helmholtz plane (i.e. the distance of closest approach) are considered within electric double layer models, where the orientational ordering of water dipoles is explicitly taken into account. It is shown that permittivity of the Stern layer is not independent of the surface charge density as it is frequently assumed in different theoretical models and simulations, but strongly depends on the magnitude of the surface charge density. Therefore, to predict the behaviour and realistic values of the surface potential and electric field, in the electrolyte solution near the charged surface, requires a surface charge density dependent permittivity of the Stern layer.