3.0 Calculation of number of particles in a Unit Cell

In a crystal atoms located at the corner and face center of a unit cell are shared by other cells and only a portion of such an atom actually lies within a given unit cell.

$1.$ A point that lies at the corner of a unit cell is shared among eight unit cells and therefore, only one eighth of each such point lies within the given unit cell.

$2.$ A point along an edge is shared by four unit cells and only one-fourth of it lies within any one cell.

$3.$ A face-centred point is shared by two unit cells and only one half of it is present in a given unit cell.

$4.$ A body-centred point lies entirely within the unit cell and contributes one complete point to the cell.

Type of Lattice point	Contribution to one unit cell
Corner	$\frac{1}{8}$
Edge	$\frac{1}{4}$
Face-center	$\frac{1}{2}$
Body Center	$1$