Local Field Effects on Dielectric Properties of Solids

Local field effects on the dielectric properties of solids have been studied for three-dimensional and two -dimensional crystals by using two kinds of dipole models: an atomic dipole model in which dipoles coincide with atom sites and a bond dipole model in which dipoles are placed along bond directions. Local fields at the dipole sites and at the interstitial sites are calculated in a self -consistent manner. Both the three and two dimensional model give results in the form of the classical Lorentz -Lorenz relation. The formulas for calculating the dipole sums have been obtained by applying the Born-Ewald method in three and two dimensions. Lorentz factors for several three and two dimensional crystal structures have been calculated. Elasto-optic (Pockels) constants have been studied for the rare gas solid Xenon. Pockels constants have also been calculated for some selected tetrahedral crystals using both dipole models.