A molecular based continuum approach for the dielectric permittivity of liquids and liquid crystals

A method for the calculation of the dielectric permittivity of isotropic and anisotropic homogeneous fluids is presented which, in the framework of the continuum approximation, adopts a realistic description of the molecular features, so overcoming some of the limits of the Onsager model. The Poisson equation for the molecular charge distribution contained in a cavity in a dielectric continuum in the presence of an external field is solved by a boundary element technique, which allows a detailed description of the cavity shape associated with a given molecular structure. The charge distribution is described in terms of point charges derived from ab initio calculations in vacuum, in addition to a set of interacting atom dipoles induced by all the electric fields experienced by the molecule in the condensed phase. The link between molecular features and bulk properties is established in a general way suitable for isotropic liquids and nematic phases, through the orientational distribution function of the mo...