Crystal Lattice Assignment Help

Space lattice or crystal latticeis a regular repeating arrangement of points in space. As it is regular repeating arrangement, to describe the space lattice completely, we can choose a small part of the lattice, which when repeated in different directions produces the complete space lattice. This small portion of the lattice is called unit cell.
Two dimensional lattices: A two dimensional lattice is a regular arrangement of points in the plane of the paper. We chemistry suitably choose four points and connect them to obtain the unit cell. In some cases, the unit cell may have an interior point also. Such unit cells are called central unit cells. The unit cell that does not contain any interior point is called primitive unit cell.

Characteristics of a crystal lattice

1. Each point in the crystal lattice represents a constituent particle which may be an atom, a molecule or an ion.
2. Each point in the lattice is called lattice point or lattice site.
3. The points are joined by lines just to represent the geometry of the lattice.

Unit cell

The smallest three dimensional portion of a complete space lattice which when repeated over and again in different directions produces the complete space lattice is called the unit cell.

Parameters of a unit cell: A unit cell is characterised by the following parameters which decide the size and shape of the unit cell:

(i) Its dimensions along the three edges a, b and c. These edges may or may not be perpendicular to each other.

(ii) Angles between the edges i.e., angle α between the edges b and c, angle β between the edges a and c and angle γ between the edges a and b.