Question: what are the coordination number for octahedral and tetrahedral sites?
Answer: It follows that there are 2 tetrahedral and 1 octahedral holes per anion in a fcc structure where the anions make the close-pack framework. Thus the coordination number for Na+ is 4 and for O2- is 8. Consequently the stoichiometry for sodium oxide is Na2O. e tetrahedral holes are filled by the small zinc ions.