Question

In a face-centred cubic (FCC) arrangement, the number of atoms per unit cell is :

• A. $8$
• B. $2$
• C. $1$
• D. $4$

Answer 1

Answer: (D)

$4$

FCC has $8$ atoms at the corners of the cube each having $\frac{1}{8}$ contribution.

Therefore, the total number of atoms at the corners$=\frac{1}{8}\times 8=1$

Besides, it has $6$ atoms at $6$ faces each having $\frac{1}{2}$ contribution.

Therefore, the total number of atoms at the faces $=\frac{1}{2}\times 6=3$

This implies that the total number of atoms in FCC $=1+3=4$