Question

In a cubic close packed structure, fractional contributions of an atom at the corner and at the face in the unit cell are, respectively

• A. $1/8$ and $1/2$
• B. $1/2$ and $1/4$
• C. $1/4$ and $1/2$
• D. $1/4$ and $1/8$

Answer 1

Answer: (A)

The cubic lattice possesses $8$ atoms on the corner.
$\therefore $ Fractional contribution by of atoms at the corner = $\frac{1}{8}.$
Each atom located at the face centered of ccp structure is shared between two adjacent unit cell and only $\frac{1}{2}$ of each atom belongs to a unit cell.
Thus, fractional contribution of each atom at face = $\frac{1}{2}$