Intermetallic phases structure families

Structure trivial names and Strukturbericht symbols As a conclusion to the presentation of the rational nomenclature and symbolism of the intermetallic phases, it must be mentioned that a number of trivial names and symbols have been used and, due to historical reasons, are still in use both as indicators of a single phase in specific systems, or as descriptors of certain structural types or of families of different interrelated structural types. 

On the basis of the Periodic Table, topics of intermetallic systematics will be presented in the next chapter. In the present chapter the Periodic Table will be revisited and its structure and subdivisions summarized. In relation also to some concepts previously presented, such as electronegativity, Mendeleev number, etc. described in Chapter 2, typical property trends along the Table will be shown. Strictly related concepts, such as Periodic Table group number, average group number and valence-electron number will be considered and used in the description and classification of intermetallic phase families. 

AlB2-type variants and derivative structures. A number of A1B2-type related structures are here presented in order to emphasize the role that structural characteristics such as those present in the A1B2 type may play in a variety of intermetallic phases and to illustrate an example of a structure family containing numerous members interrelated by various kind of more or less large deformations or substitutions. Reference to a seminal paper by Gladyshevskii et al. (1992) will especially be made. 

Since the X-ray diffraction studies of Zintl et al. , these members of the family of intermetallic compounds have been of special interest because some of their chemical properties are unusual for intermetallic phases. Many experimental investigations have been reported for binary and ternary B32 type compounds. Besides the crystal structure " , the thermodynamic behavior , electrical conductivity ", magnetic susceptibility , NMR data elastic constants - and optical properties have been studied. Additionally for LiAl electrochemical investigations have been performed in view of the recent interest in fast ionic conductors " . ... 

One of the important series of rare-earth intermetallic compounds are those which possess the ThMni2-type structure. Generally, these compounds form as ternary phases with only a handful of binary compounds known to exist. As pointed out in the review by Suski (chapter 149) there are two distinct subgroups in this family of compounds those with a relatively low content of transition element (Fe, Co and Ni) and those with a high content of these metals. The first group of compounds are stabilized by Al, Ga and In,... 

The first solution to this problem was produced phenomenologically by Mooser and Pearson. The solution for A B compounds is reproduced in Figure 9. Similar solutions apply not only to A"B semiconductors and insulators, but also to many intermetallic compounds including transition metals. This work provides the first step toward explaining structural and phase transitions in chemically homologous families of binary crystals. It has made the question of the proper treatment of chemical bonding in crystals susceptible to theoretical analysis, whereas formerly work based on mechanical models (ionic compounds) or quantum mechanical perturbation theory (nearly-free-electron metals) made the same problem appear insoluble. 

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