Crystal Chemical Characterization of Inorganic Structure Types

Abstract

In this chapter are described some of the general structural relationships wh ich have been observed between inorganic structure types. In the Main Data- Table condensed crystal chemical information about the individual structure types can be found in the "information" records VALEL and DESCR and a limited number of related structure types are mentioned in the RELAT record. It is weil known that structures with very different compositions, cell dimensions andlor very different symmetries may show many structural similarities. For example, particular structures can be grouped in a structure series built up of similar elementary building segments, or can be rationalized according to valence electron concentration rules (tetrahedral structures, polyanionic valence compounds, structures with tetrahedral anion complexes etc.). This chapter is intended to give an overview of these relationships through additional comments, references, diagrams, structure drawings etc., presented in more than 50 tables, labelIed by a code consisting of a letter and a number. The same codes are reported in the Main Data- Table under the TABLE record (see Chapter 5.2.). In this way, when the reader is interested in a particular structure type, he can get more information on related structures by consulting the crystal chemical tables. The structure types in tables starting with the same letter have been analyzed under a similar crystal chemical point of view, ;.e.: A: Structures with dose packed layers B: Structures of compounds where valence electron considerations can be applied C: Structures with intergrown slabs D: Structures with intergrown columns or blocks E: Structures with particular atom coordinations and linkages F: Deformation, substitution, filled-up and vacancy derivatives.Some of the structure types can be considered under different aspects and may be found in different tables. In the case of the B tables it should be noted that the valence electron considerations apply to compounds having a particular structure type. Correlations exist here between available valence electrons and structural features and the listed structure types are, with few exceptions, found only with compounds having the expected number of valence electrons. The complete list of table titles can be found in the Contents at the beginning of the book.We would like, however, to stress the point that it is not possible to consider here all structural relationships which have already been reported in the literature. The information on the structural relationships treated in this chapter is not exhaustive and has a certain personal note to it.Crystal chemical formulae and short symbols used here for describing structural relationships

Physical properties of non-centrosymmetric Ni2Zn11

“…a Crystal structure data are standardized using the program Structure Tidy[20]. b Anisotropic atomic displacement parameters U ij [nm 2 ] Â10 À2 .Z.…”

The crystal structure and magnetic properties of the GdCrxAl12−x (x=3.5 and 4.0) intermetallics

“…The background was refined with a polynomial function. The title ternary intermetallic compound crystallizes in tetragonal space group I4/mmm (Pearson symbol tI26), with ThMn 12 structure type (or CeMn 4 Al 8 type with x = 4.0) [14]. The results of the crystal structure determination for the GdCr x Al 12−x with x = 3.5 and x = 4.0 are summarized in Table 1.…”

The crystal structure of the new Gd5CoSb2, Gd5NiSb2 and Gd5Au2Sb ternary phases

“…The Gd1, Gd2, Gd3, Gd4, Co(Ni) and Sb atoms are surrounded by 9, 11, 9, 12, 7 and 9 neighbours. The ternary Gd 5 Au 2 Sb compound belongs to the Mo 5 B 2 Si structure type (ordered variant of Cr 5 B 3 type) [9]. Gd atoms occupy the positions of Mo atoms, the Au atoms occupy the site of B atoms and atoms of Sb occupy the positions of Si atoms in this structure.…”