Density is given by
d = (z*M)/(a3*NA)
given that a1 = 3.5 A0 and a2 = 3.0 A0
No of atom per unit cell of fcc z1 = 4
No of atom per unit cell of fcc z2 = 2
Sonratio of density of fcc and bcc
d1/d2 = (z1/z2)*(a2/a1)3 = (4/2)*(3/3.5)3 = 2*(6/7)3 =432/343.
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