The modification of chemical bonds that was caused by an impurity which occupied a lattice site was investigated. The electronic structures of normal and doped crystals were calculated, within the cluster approximation, by using the self-consistent scattered-wave method. A wide range of impurities, which included non-transition elements and transition or rare-earth metals, was considered. The analysis of a modification of the chemical bond in an impurity cluster indicated possible distortions of the crystal structure near to an impurity center. These predictions agreed well with experimental data. It was shown that the reconstruction of an impurity center was probabilistic in nature. The probability of reconstruction increased with the degree to which the chemical bond was modified by an impurity. It increased under any external distortions of the crystal structure. It was found that there were 2 basic types of distortion, and the relationship between the symmetry of the reconstructed center and its charge state was considered.

D.E.Onopko, N.T.Bagraev, A.I.Ryskin: Fizika Tverdogo Tela, 1995, 37[8], 2376-97 (Physics of the Solid State, 1995, 37[8], 1299-310)