Structure of a mixed oxide is cubic close - packed (c.c.p). The cubic unit cell of mixed oxide is composed of oxide ions. One fourth of the tetrahedral voids are occupied by divalent metal A and the octahedral voids are occupied by a monovalent metal B. The formula of the oxide is:
As we learnt in
No. of atoms(z) for end centered unit cell -
Lattice point: at corners and one pair of opposite face centers.
For end centered cubic, z=2
Given that its a c.c.p and unit cell is composed of oxide ions.
B = 4
Summing up, the formula is