The display shows an idealised unit cell (Space group 216 F-43m).
The cubic cell lengths used were a=b=c=8.0858A.
These are not the usual values quoted and come from what seems to be
an overlooked paper in Proc. Roy. Soc., 1983, 386, 333-245.
Their crystallographic evidence suggests that a better fit of the data
comes from F-43m, rather than the
often quoted Fd3m centrosymmetric space group.
Spinel is the name given to the mineral
MgAl2O4. It has a common structural
arrangement shared by many oxides of the transition metals
with formula AB2O4.
In the normal pattern the oxygens (red) form a
cubic close packed (ABCABC or face centred) array and the
Mg(II) (A(II)-green) and Al(III) (B(III)-silver) sit in tetrahedral
(1/8 occupied) and octahedral (1/2 occupied) sites in the lattice, giving
a Unit Cell with 8 Mg's, 16 Al's and 32 O's.
An inverse spinel is an
alternative arrangement where the divalent ions swap with
half of the trivalent ions so that the
M(II) now occupy octahedral sites
Complexes that share this structure include..
many of the first row TM oxides and sulfides
One method of predicting whether a structure will be normal or inverse
is to calculate Octahedral Site Preference Energies for both the A(II)
and B(III). The ion with the more stable energy is predicted to fit into
the octahedral site.
However, see J. Am. Chem. Soc., 1982, 104, 92-95 for a different
method that does NOT involve OSPE calculations.
For alternate views of spinels,
and check out the following sites;
University of Le Mans.
Information is available to show how the
individual structural pages were created.
Return to the
structure of binary salts introductory page.
Return to Chemistry, UWI-Mona,
Copyright © 2000-2014 by Robert John
Lancashire, all rights reserved.
Created and maintained by Prof. Robert J.
The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica.
Created March 2000. Links checked and/or last modified
27th November 2014.