By using the chemical bond theory of dielectric description, the chemical bond parmneters of (Hg, Pb)-1223 were calculated. The results show that the (Ba, Sr)-O and Ca-O types of bond have higher ionic character, while the Or-O and (Hg, Pb)-O types of bond have more covalent character. Mshauer isomer shifts of STFe and mSn doped in (Hg, Pb)-1223 were calculated by using the chemical eaviromncntal factor, he, defined by covalency and electronic polarizabih'ty. Four valence state tin and three valence iron sites were identified in STFe and mSn doped (Hg, ffo)-1223 super-conductor. It can be conduded that all of the Fe atoms substitute the Cu at square planar Cu(1) site, whereas Sn profers to substitute the square pyramidal Cu(2) site.

Barium hexaferrite was synthesized by chemical co-precipitation. Its Mossbauer spectra were obtained. A semi-empirical model, based on the Phillips theory of bonding, has been developed for quantitative explanation of the M

The nature of the impurity centre in LiNbO3 has been a subject of intense discussion in recent years. A semi-empirical model, based on the Phillips theory of bonding, has been developed to provide a quantitative explanation of the nephelauxetic effect of Cr3+ ions and M

By usingthe chemical bond theory of complex crystals, the chemical bond properties of REBa2Cu3O7 (RE=Eu, Y) were calculated. The calculated covalencies for Cu(1)-O and Cu(2)-O bond in REBa2Cu3O7 compounds are 0.41 and 0.28 respectively. Mossbauer isomer shifts of 57Fe doped, and 119Sn doped in REBa2Cu3O7-x were calculated by using the chemical environmental factor, he, defined by covalency and electronic polarizability. Four valence state tin ion and iron ion sites were identified in 57Fe and 119Sn doped REBa2Cu3O7 x superconductors.

By using the chemical bond theory of dielectric description and electronic structure of 3d elements, the mechanism of nephelauxetic effect is studied, and the main factors responsible for this effect are identified. These are: the covalency of chemical bond, polarizabilities ofligand bond volume for the host and the valence and slain state of the center ion. Relationships between these factors are given, and the results are discussed.