**Crystal lattice**

A crystal lattice is an array of points representing atoms, ions, or molecules of a crystal, arranged at different sites in three-dimensional space.

A crystal is composed of atoms, ions, or molecules. In crystalline solids, these atoms, ions, or particles lie at definite positions in space. These positions are represented by points in a crystal. These points are called lattice points or lattice sites.

This setup of factors in a crystal is called crystal lattice or space lattice.

**Unit Cell**

The tiniest part of the crystal lattice has all the characteristic functions of the entire crystal and is called a unit cell.

It means that a unit cell of a crystal lattice is the tiniest block or geometric figure, where the whole crystal can be built up by duplicating it in three dimensions.

It reveals the structural properties of a provided crystal. The total information concerning the crystalline framework exists within a unit cell which duplicates itself in three dimensions to create a crystal.

If we understand the specific arrangement of atoms in a unit cell, we as a matter of fact understand their position in the entire crystal. The measurable factors of a crystal lattice are reasoned from the size and shape of the unit cell.

There are three, unit cell lengths **a, b, c,** and three, unit cell angles**α****, ****β,**** and γ**. These six parameters of the unit cell are called unit cell dimensions or crystallographic factors.

**Classification of Crystal System**

A crystal system may be identified by the dimensions of its unit cell along its three edges or axes, a, b, c as well as three angles in between the axes α, β, and γ. There are seven crystal systems. These 7 crystal systems are called as follows:

**1. Cubic system**

In this system, all three axes are of equal size and all go to appropriate angles to one another.

**2. Tetragonal system**

In this system, two axes are of equal size, and the third axis is either shorter or larger than the other two. All angles are 90 °.

**3. Orthorhombic Or Rhombic System**

All three axes are of unequal size and all go to the right angle to each other.

**4. Monoclinic System**

All the three axes are of unequal size; two of these axes go to the right angle to each other while the third angle is greater than 90 °.

**5. Hexagonal System**

In this system, two axes are of equivalent length and are in one plane making an angle of 120° with each other. The third axis which is different in size than the other two is at a right angle to these two axes.

**6. Rhombohedral System or Trigonal System**

All the three axes are of an equivalent size like the cubic system but the three angles are not equivalent as well as exist in between 90 ° and 120 °.

**7. Triclinic System **

All the three axes and the three angles are unequal as well as none of the angles is 90 °.