Let the edge length of the cube be ‘a’ and the radius of each particle be r.
So, we can write:
Now, volume of the cubic unit cell
We know that the number of particles per unit cell is 1.
Therefore, volume of the occupied unit cell
Hence, packing efficiency
(ii) Body-Centred Cubic
It can be observed from the above figure that the atom at the centre is in contact with the other two atoms diagonally arranged.
From , we have:
Again, from , we have:
Let the radius of the atom be r.
Length of the body diagonal,
Volume of the cube,
A body – centred cubic lattice contains 2 atoms.
So, volume of the occupied cubic lattice
(III) Face-centred cubic
Let the edge length of the unit cell be 'a' and the length of the face diagonal be .