Question

What is ratio of number of atom per unit cell in the bcc
and fcc?

Answer 1

Explanation:

In a FCC lattice there rer 8 atoms at eight corners and 6 at face centers,

Now each corner contributes to eight cells so per unit cell contribution is (1/8) × 8=1 atom.

Now similarly each face center contributes to two unit cells so contribution per unit cell by six face centers is equal to (1/2) × 6=3 atoms. Hence total no. of atoms per unit cell of FCC lattice is (1+3)=4 atoms.

For BCC-

A bcc has one atom in center and (1/8) th part of 8 corner atoms i.e 1 atom.

In total there are 1+1=2 atoms.

Hence the ratio = BCC:FCC = 2:4 = 1:2