Bravais Space Lattices:

In 1848, Bravais had shown that under the seven systems of the crystals given above; there could exist only 14 different lattices. These are called Bravais lattices.

For a cubic system, three types of lattices are possible viz.

(i) Primitive or simple cubic cell

(ii) Body centered cubic cell

(iii) Face centered cubic cell

In a primitive or simple cubic cell, each corner represents a lattice point. It means there are eight lattice points in a simple cubic cell.

In the body centered cubic cell, one lattice point is situated at each corner of the cube and one lattice point is at the centre of the cubic cell.

In the face centered cubic cell, one lattice point is situated at each corner of the cube and also one lattice point at the centre of the each face of the cubic cell.

Examples

(1) CaCl is an example for simple cubic cell.

Here, a = b = c = 4.11 Å.

(2) α-iron is an example for body centered cubic cell.

Here, a = b = c = 2.86 Å.

(3) NaCl is an example for face centered cubic cell.

Here, a = b = c = 5.63 Å.