ELECTRONIC-STRUCTURE OF INTERFACES AND EXTENDED DEFECTS IN IONIC COVALENT CRYSTALS

A consistent description is given in terms of the Green function metho d of electronic states associated with interfaces and extended defects in ionic covalent crystals. Closed expressions are derived for calcul ating the density and dispersion of impurity states. These expressions do not require the knowledge of wave functions of electrons, rather t hey operate with a limited number of Fourier transforms of Green funct ions of an ideal crystal. Formulas are given for calculating the elect rostatic part of the potential at the defect and on the surface allowi ng an effective summation of lattice sums. The theory is illustrated b y the example of an ideal chain of oxygen vacancies in AMO3-type oxide s.