In a cubic closed packed structure of mixed oxide, the oxide ions are in CCP arrangement 1/6 of tetrahedral voids are occupied by cations A and 1/2 of octahedral voids are occupied by cations B. The formula of the oxide is

Oxide ion form CCPNumber of effective O atoms = 8 corners X 1/8 per corner atom share + 6 faces X 12per face center atom share                                               = 8 X 1/8 + 6 X 12=4Each atom create 2 tetrahedral voids and one octahedral voidsNumber of effective A atoms = 16X 8 (tetrahedral voids) =43ANumber of effective B atoms =12 X 4 ( octahedral voids) = 2BFormula of the compound is A43B2O4 =A2B3O6