A face centred cubic lattice of a single type of atoms has same defects and its one corner and one face centre is left unoccupied per unit cell. Calculate the packing fraction of such solid.

Explanation

To calculate the packing fraction of a face-centered cubic (FCC) lattice with one corner atom and one face-centered atom missing, we can follow these steps:

### Step 1: Determine the number of atoms per unit cell
In a face-centered cubic lattice, normally:
- There are 8 corner atoms, each contributing \( \frac{1}{8} \) of an atom to the unit cell.
- There are 6 face-centered atoms, each contributing \( \frac{1}{2} \) of an atom to the unit cell.

However, in this case:
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