Premium
La 4 Br 2 Al 5 and Ce 4 Br 2 Ga 5 : Three‐dimensional Metal Networks Embedded in Condensed Ln 6 Trigonal Prisms
Author(s) -
Zheng Chong,
Mattausch Hansjürgen,
Oeckler Oliver,
Nuss Jürgen,
Simon Arndt
Publication year - 2003
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200300214
Subject(s) - isostructural , crystallography , halide , cerium , metal , chemistry , lattice constant , space group , valence (chemistry) , crystal structure , halogen , magnetic susceptibility , materials science , physics , x ray crystallography , inorganic chemistry , diffraction , alkyl , organic chemistry , optics
La 4 Br 2 Al 5 and Ce 4 Br 2 Ga 5 are metal‐rich and feature Al or Ga centered Ln 6 (Ln = La, Ce) trigonal prisms. The packing of these prisms is unique and characterizes a new variation in reduced rare‐earth halides. The prisms fuse into dimeric units which in turn form rectangles parallel to the a ‐ b plane. They then stack in the [0 0 1] direction, creating channels along the c ‐axis. The halides occupy these channels, while Al or Ga atoms join to a three‐connected, three‐dimensional network encircling these channels. The title compounds represent a new structure type, crystallizing in the space group Cmmm (No. 65) with lattice constants a = 16.115(3) and 15.796(3)Å, b = 17.206(3) and 16.795(3), c = 4.3280(9) and 4.2344(8)Å, respectively for La 4 Br 2 Al 5 and Ce 4 Br 2 Ga 5 . An isostructural, however nonstoichiometric and disordered phase La 4.15 Br 2 Ga 4.69 also exists with a = 15.902(1)Å, b = 17.034(1)Å, and 4.2612(3)Å. Computational analysis reveals that they belong to the class of reduced valence rare‐earth halides. However, because of the extended interaction between Ln and M, the conduction band of these compounds is partially occupied. Conductivity and magnetic susceptibility measurements confirm the metallic nature of these compounds, and reveal Cerium to be trivalent as expected.