Which type of defect does not affect the density of the crystal ?

Which stoichiometric defect decreases the density of the crystal?

Examine the given defective crystal : {:(X^(+),Y^(-),X^(+),Y^(-),X^(+)),(Y^(-),O,Y^(-),X^(+),Y^(-)),(X^(+),Y^(-),X^(+),O,X^(+)),(Y^(-),X^(+),Y^(-),X^(+),Y^(-)):} Answer the following questions. How does this defect affect the density of the crystal?

Which type of crystal defect increases the density of a solid ?

Why does Frenkel defect not change the density of AgCl crystal?