XY3 has ccp arrangement for element Y, X occupies 33% octahedral voids. In case of close packed arrangement there is one octahedral and two tetrahedral voids corresponding to each atom constituting the lattice. Atom Y adopt ccp arrangement and there are 2 tetrahedral sites per atom of Y. Atom X occupies one octahedral void corresponding to each atom constituting the lattice. Total there are 3 voids In % X occupies