Compounds with CsCI structure

Compounds with CsCI structure 75 6. Hard magnetic materials 197... 

Much information is available concerning the magnetic properties of the equiatomic RB compounds with the CsCI structure. The causes of the popularity of these compounds are perhaps the wide range of possible non-magnetic... 

Thus increased covalent bonding resulting from Fajans-type phenomena can lower the transition temperatures. For example, the alkali halides (except CsCI. CsBr, and Csl) and the silver halides (except Agl) crystallize in the NaCI structure. The sizes of the cations are comparable Na+ = 116 pm. Ag+ 129 pm. K+ = 152 pm, yet the melting points of the halides are considerably different (Table 8.6). The greater covalent character of the silver halide bond (resulting from the electron configuration) compared with those in the alkali halides helps stabilize discrete AgX molecules in the liquid and thus makes the melting points of the silver compounds lower than those of the potassium compounds. A similar comparison can be made between the... 

An important simplification in the study of intermetallic compounds is provided by the concept of isotypism. Several compounds have the same composition, the same structure with the same coordination polyhedra We say that they are isotypic and identify a "structure type". For example, nearly 280 CsCI-type and more than 150 MngSis-type binary phases are reported in the literature. We can take advantage from this fact and, chosen a given composition, try a systematization of the structural types. In other words, we can build a map where are retried the representative points of all the isotypic phases. If the coordinates of the map are correctly chosen, we should be able to define a region for the occurrence of each structure type. It is clear that such a map could be a useful guide in synthesizing new materieils with a desired structure and with desired physical properties, but it is also clear that the approach is phenomenological and based on already known experimental data. 

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