ffiffi ffi
2
p
a ¼ 4R or a ¼ 2
ffiffi ffi
2
p
R
Therefore, the volume of the unit cell is
V ¼ a
3
¼ 16
ffiffi ffi
2
p
R
3
¼ 16
ffiffi ffi
2
p
(for R ¼ 1Þ
Further for fcc, the number of spheres (atoms) in the unit cell is 4, then the
volume occupied is
Fig. 1.35 Critical radius ratio
in sc
Fig. 1.36 Critical radius ratio
in fcc
1.5 Close Packing of Identical Atoms (Spheres)
33
2
p
a ¼ 4R or a ¼ 2
ffiffi ffi
2
p
R
Therefore, the volume of the unit cell is
V ¼ a
3
¼ 16
ffiffi ffi
2
p
R
3
¼ 16
ffiffi ffi
2
p
(for R ¼ 1Þ
Further for fcc, the number of spheres (atoms) in the unit cell is 4, then the
volume occupied is
Fig. 1.35 Critical radius ratio
in sc
Fig. 1.36 Critical radius ratio
in fcc
1.5 Close Packing of Identical Atoms (Spheres)
33