Types of unit cell

There are four types of unit cell, distinguished by where the constituent particles are located within the cell.

i. Primitive or simple unit cell : Constituent particles are present at the eight corners of the unit cell only.

ii. Body-centred unit cell : In addition to the particles at the eight corners, one particle is present at the centre of the body of the unit cell.

iii. Face-centred unit cell : In addition to the particles at the eight corners, one particle is present at the centre of each of the six faces of the unit cell.

iv. Base-centred unit cell : In addition to the particles at the eight corners, one particle is present at the centre of each of any two opposite faces of the unit cell. …