Multipole Theory of the Polarization of Solids by Point Defects. I. Dipole Approximation

The electronic structure of solids is investigated where the electronic density is localized on structure elements (atoms, molecules, bonds). For these solids containing point defects the Schrödinger equation is obtained in the framework of a molecular cluster model taking self‐consistently into account the polarization of the rest of the solid outside the cluster. The polarization is considered in terms of multipole moments on structure elements induced by the defects neglecting exchange interactions. In the first part of the paper the general theory developed is applied to ionic crystals in the dipole approximation. The way to use the cluster symmetry in polarization calculations is also analyzed.