1. Chromium has BCC structure. Its atomic radius is 0.1249 nm. Calculate the free volume/unit cell.
(Set-4–May 2007), (Set-4–Sept. 2006)
Sol: Given data are
Atomic radius of chromium, r = 0.1249 nm.
Free volume/unit cell = ?
If ‘a’ is the BCC unit cell edge length, then the relation between ‘a’ and ‘r’ is
Volume of unit cell, V = a3 = (0.28845)3 nm3
= 0.024 nm3
Number of atoms in BCC unit cell = 2
Hence volume of atoms in unit cell,
Free volume/unit cell = V – v = 0.00767 nm3
2. Lithium crystallizes ...