Density functional approach to the effective interaction between charges within dielectric cavities

A variational approach based. on. a functional of the polarization charge density at interfaces between different dielectric bodies is-used to calculate the energy of electrostatic interaction between two electric charges embedded in either two spherical dielectric cavities or in one spheroidal cavity. An effective, distance-dependent dielectric function is extracted from these results, which is exact within the macroscopic theory of dielectrics. We show that different dielectric functions must be associated with pairs of equally or oppositely charged ions and with pairs of ions in cavities of the same or differing radii.