# Calculation of density of unit cell

The work of Auguste Bravais in the early 19th century revealed that there are only fourteen different lattice structures (often referred to as Bravais lattices). These fourteen different structures are derived from seven crystal systems, which indicate the different shapes a unit cell take and four types of lattices, which tells how the atoms are arranged within the unit.

We can unambiguously describe a piece of wallpaper by specifying the size, shape, and contents of the simplest repeating unit in the design. We can describe a three-dimensional crystal by specifying the size, shape, and contents of the simplest repeating unit and the way these repeating units stack to form the crystal. The simplest repeating unit in a crystal is called a unit cell. Each unit cell is defined in terms of lattice points the points in space about which the particles are free to vibrate in a crystal.

### Volumes

The volume for a unit cell is the same as the volume for any prism. Volume is equals to base area multiplied by height.

### Density (Particles)

It is seen that not all the particles are complete in the unit cell form. For the fractional particles in unit cell, its corner particles will always sum to one whole particle, its face particles will sum to three whole particles, and for the base particles will sum to one.

### Calculations of density of unit cells

density = Mass/Volume.

Related topic : Calculate Volume of Prism