Question

Give the number of lattice points in one unit cell of the following crystal structures : 

(1) Simple cubic 

(2) Face-centred cubic 

(3) Body-centred cubic.

Answer 1

Lattice points in one unit cell represent the positions of atoms, ions or molecules in the unit cell.

(1) Simple cubic unit cell : In this primitive unit cell, the lattice points are at 8 corners of the unit cell. 

Hence there are 8 lattice points.

(2) Face-centred cubic unit cell : In this unit cell, the lattice points are at 8 comers and 6 face centres.

(In cubic close packing unit cell, the lattice points are also at edge centres and body centre.)

(3) Body-centred cubic unit cell : In this, the lattice points are at 8 comers and one at body centre.