The spinel structure consists of ............

In a $A_x B_y$ crystal structure,$A^{+y}$ ions occupy all the tetrahedral voids and $B^{-x}$ ions form a $BCC$ unit cell. What is the formula of the compound?

The percentage of unoccupied volume in a simple cubic cell is (in $\%$)

In the closest packing of atoms,there are

In an $A_{x} B_{y}$ crystal structure,$A$ atoms occupy all octahedral as well as all tetrahedral voids,and $B$ atoms are at the $FCC$ lattice points. What is the formula of the compound $A_{x} B_{y}$?

Atom $X$ occupies the $fcc$ lattice sites as well as alternate tetrahedral voids of the same lattice. The packing efficiency (in $\%$) of the resultant solid is closest to