The crystallographic structure of the MA spinel was determined independently
by Bragg (2) and Nishikawa (3). It is simple cubic and belongs to space group
Fd3m with eight formula molecules in one cubic unit cell. The oxygen ions
form an almost perfect cubic close-packed array with the metal ions distributed
among the resulting positions of fourfold and sixfold oxygen coordination. The
maximum number of possible tetrahedral and octahedral sites is 64 and 32,
respectively. The coordinates of the ionic positions for this space group are 8 positions
of fourfold oxygen coordination at 8a, 16 positions of sixfold oxygen
coordination at 16d, and 32 positions at 32e.