If a crystal changes from fcc to bcc , then calculate the ratio of density between fcc and bcc ? THERE IS NO CHANGE IN THE RADIUS OF THE ATOM.

We know,

D = Z m/a3NA

Where,

D is the density of the crystal

Z is the number of atoms in a unit cell  ( 4 for FCC and 2 for BCC)

m is the atomic mass

a is the edge length of the cube

NA is the  avagadro‚Äôs number

 

Let D1 is the density for FCC structure and D2 be the density for BCC structure

Therefore,

  • -2

D=Z m/a3NA

There is change in only Z.For fcc it is 4 & bcc 2

So the ratio is 4:2  or  2: 1

  • -5
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