Relation between the local field at large distances from a charge or dipole and the dielectric constant.

The local field at large distances from a charged or dipolar impurity in a nonpolar polarizable fluid is related to the dielectric constant of the medium. The predicted local field agrees accurately with molecular dynamics results. In contrast, the usual continuum theory prediction is only accurate to first order in the polarizability and leads to serious error for realistic values of the polarizability. At smaller distances these relations cannot be used to define a physically reasonable local dielectric constant and consequently the local field is more satisfactorily described in terms of a screening function.