Superstructures and other related structures

In a substitutional solid solution AA there is random arrangement of A and A atoms in equivalent positions in the crystal structure. If on suitable heat treatment 

The same set of positions occupied in a regular way by atoms of two or more kinds A and A  

A and A occupy different Both sets of equivalent positions 

As regards the formulae the relation is similar to that between the parent structure and superstructure except that we have 

Difference between the various sets of equivalent positions (1) Atoms o(different metals (2) Atoms of same metal in different oxidation states (3) Atoms of same metal in same oxidation state 

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