Question

A metal crystallizes into two cubic phases, face centred cubic (fcc) and body centred cubic (bcc), whose unit cell lengths are 3.5 and 3.0 , respectively. Calculate the ratio of densities of fcc and bcc.

Answer 1

We have, F.C.C unit cell length =3.5 ,

B.C.C unit cell length= 3.0

Now no. of atoms for F.C.C(n1 )=4;

V1 =a3 = (3.5 x 10-8)3

Now no. of atoms for B.C.C(n1 ) =2