1.5 Crystal lattices and unit cell

Crystal lattices: - The regular repeating of 3-D figure, is called Crystal lattices.

·         Some character of crystal lattices

1.       Crystal lattices are in 3-D figure.

2.       All points in crystal lattice is called lattice.

3.       Particles are present on each lattice point.

Unit cell :- The small part of crystal lattice which is in 3-D figure that is called Unit cell.

OR

The smallest group of atoms which has the overall symmetry of a crystal, and from which the entire lattice can be built up by repetition in three dimensions.

Type of Unit Cell :-  On the basis of axial angle and edge length unit cell or crystal system are of 7 types.

Type of unit cell on the basis of lattice point.(for Cubic)

1.      S.C.C. (Simple Centre Cubic unit cell):- Four lattice point on four corners.

2.      Centre cubic unit cell

• E.C.C.(end-centered unit cell) : an extra lattice point is centered in each of two opposing faces of the cell
• F.C.C.(face-centered) : an extra lattice point is centered in every face of the cell
• B.C.C.(body-centered) : an extra lattice point is centered in the exact middle of the cell