Number of atoms in face-centred cubic (fcc) unit cell :
In this unit cell, there are 8 atoms at 8 corners and 6 atoms at 6 face centres.
Each comer contributes 1/8th atom to the unit cell, hence due to 8 corners,
∴ Number of atoms present in the unit cell = (1/8) X 8 = 1
Each face centre contributes half of the atom to the unit cell, hence due to 6 face centres,
Number of atoms =1/2 x 6 = 3.
Total number of atoms present in fcc unit cell = 1 + 3 = 4.
Hence the volume of the unit cell is equal to the volume of four atoms.
