A THEORETICAL-STUDY OF THE FORMATION AND AGGREGATION OF VACANCY IMPURITY DIPOLES IN DI-VALENTLY DOPED ALKALI-HALIDE CRYSTALS

Computer simulation techniques based on generalized Mott-Littleton methods have been used to investigate defect structures in systems resulting from the incorporation of Mn**2** plus , Cd**2** plus and Pb**2** plus ions into NaCl, KCl and KBr crystals. Two-body interionic potentials based on the simple shell model were used in the calculations. The (110) nearest-neighbor (n. n. ) and (200) next-nearest neighbor (n. n. n) simple impurity-vacancy dipoles were found to be of comparable stability, although definite trends with ion size are evident, whereas the (211) complex invariably is found to be less stable. The additional binding energies which arise when the n. n. and n. n. n. dipoles aggregate into a variety of dimers, trimers and tetramers have been calculated, as has the stability of the Suzuki phases.