The adsorption of dipoles at a wall in the presence of an electric field: The RLHNC approximation

Abstract

The adsorption of dipolar hard spheres in the presence of an external electric field has previously been studied within the context of the mean spherical approximation. In order to quantify the significance of the physical trends found above, the problem is solved within the higher order closure rules afforded by the linearized hypernetted chain approximation. Exact expressions for the reduced dipole moment and the electric field strength are derived using only the asymptotic forms of the direct correlation functions. It is found that the favorable orientational correlations between the dipolar hard spheres and the wall are underestimated by the mean spherical approximation. This is emphasized in the enhanced adsorption of the dipolar species (at the wall itself) for dipoles oriented close to the direction of the field. However, the nonphysical features of the mean spherical approximation (manifested in the negativity of the density profile) are not fully rectified by the use of the linearized hypernetted chain approximation.