One such arrangement by representing the particles with points is shown below:
fig 2.1
Such a regular arrangement of the constituent particles of a crystal in a three dimensional space is called crystal lattice or space lattice.From the complete space lattice, it is possible to select a smallest three dimensional portion which repeats itself in different directions to generate the complete space lattice. This is called a Unit Cell.
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.
The size and shape of a unit cell is determined by the lengths of the edges of the unit cell (a, b and c) and by the angles a, b and g between the edges b and c, c and a, and a and b respectively.If we take into consideration, the symmetry of the axial distances (a, b, c) and also the axial angles between the edges (a, b and g), the various crystals can be divided into seven systems. These are also called crystal habits.
