The vacant space in bcc lattice unit cell is
- 48%
- 23%
- 32%
- 26%
Answer
(3) 32%
Solution
In a bcc unit cell, Z = 2 and the atoms touch along the body diagonal: 3 a = 4r
⇒ Packing efficiency = 2 43 r3a3 100
= 2 43 r3 ( 4r 3 )3 100
= 3 8 100 68\%
∴ Vacant space = 100 - 68 = 32\%
Answer: (3)