Packing efficiency

Just like coordination number, packing efficiency gives a quantitative measure of how tightly the particles of a crystal are packed. Packing efficiency is defined as the fraction, expressed as a percentage, of the total volume of a unit cell that is actually occupied by the spheres (particles) it contains: $\text{Packing efficiency} = \dfrac{\text{volume occupied by particles in unit cell}}{\text{total volume of unit cell}}\times100$ The remaining, unoccupied fraction of the cell's volume is the void volume -- empty space between the packed spheres. The next three subsections derive the packing efficiency for each of the three cubic lattices in turn (simple cubic, body-centred cubic, and face-centred cubic/ccp/hcp), ea …