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Q.
Calculate the number of atoms in a cubic unit cell having one atom on each corner and two atoms on each body diagonal.
The Solid State
Solution:
There are $8$ corners in a cubic unit cell and each has one atom shared by $8$ cubic unit cells.
$8$ corner $\times 1 / 8$ atom per unit cell $=1$ atom
There are four body diagonals in a cubic unit cell and each has two body centre atoms.
So, $4 \times 2=8$ atoms
Therefore, total number of atoms per unit cell
$=1+8=9$.