How many tetrahedral voids are present in $0.4 \ mol$ of a compound that forms an $hcp$ structure?

If $0.5 \ mol$ of a metal forms a hexagonal close-packed structure,the total number of voids and tetrahedral voids respectively in $mol$ are

Explain the formation of voids during the transition from a two-dimensional hexagonal close-packed layer to a three-dimensional close-packed structure.

When sodium is heated above $1000 \ K$,its crystal structure changes from $bcc$ to $fcc$. Assuming the metallic radius of the atom remains unchanged,the ratio of the fraction of volume occupied by atoms in $bcc$ and $fcc$ structures will be .......

The stacking pattern in a body-centered cubic $(bcc)$ lattice is of the type............

An alloy of metals $A$,$B$,and $C$ is found to have $A$ constituting a $ccp$ lattice. If $B$ atoms occupy the edge centers and $C$ is present at the body center,the formula of the alloy is: