Skutterudite



Skutterudite is a naturally occurring compounds isostructural with the mineral.

The skutterudite mineral

  Skutterudite is a arsenic.

The mineral has a bright metallic luster, and is tin white or light steel gray in color with a black streak. The specific gravity is 6.5 and the pyrite. The arsenic content gives a garlic odor when heated or crushed.

It was discovered in Skuterud, Norway, in 1845. Smaltite is a synonym for the mineral. Notable occurrences include Cobalt, Ontario , Canada, Skuterud, Norway, Franklin, New Jersey in the United States, and in other cobalt and nickel mining areas around the world. The rare arsenide minerals are classified in Dana's sulfide mineral group, even though it contains no sulfur.

The skutterudite crystal structure

 

The crystal structure of the skutterudite mineral was determined in 1928 by Oftedahl to be cubic, belonging to unit cell can be considered to consist of eight smaller cubes made up of the Co atoms. Six of these cubes are filled with (almost) square planar rings of As, each of which is oriented parallel to one of the unit cell edges, see image on the right. The As atoms then form octahedra with Co in the centre.

In crystallographic terms, the Co atoms occupy the 8c sites, while the As atoms occupy the 24g sites. The position of the Co atoms within the unit cell is fixed, while the positions of the As atoms are determined by the parameters x and y. It has been shown that for the As-rings to be fully square, these parameters must satisfy the Oftedahl relation x+y=1/2. Any deviation from this relation yields a rectangular configuration of the As atoms. Indeed, this is the case for all known compounds with this structure, and it should be noted that the As atoms then do not form perfect octahedra.

Together with the unit cell size and the assigned space group, these two parameters fully describe the crystal structure of the material which is often referred to as the skutterudite structure.

References

  • Dana's Manual of Mineralogy ISBN 0-471-03288-3
  • A. Kjekshus and T. Rakke. Compunds with skutterudite type crystal-structure .3. Structural data for arsenides and antimonides. Acta Chemica Scandinavica Series A 28 (1): 99-103 1974.
  • Mineral galleries
  • Mindat.org
  • Webmineral.com

See also

 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Skutterudite". A list of authors is available in Wikipedia.