Definition of Unit Cell:Unit cell is the smallest repeating structural unit of acrystalline solid(orcrystal lattice) which when repeated in different directions produces thecrystalline solid(lattice).

When the **lattice** points of a space **lattice**, are joined by straight lines a large number of parallelepiped are formed. Each parallelepiped is the smallest and a complete unit. When these units are repeated in space, a **crystal lattice** is obtained. This three dimensional smallest group of **lattice** points is known as **unit cell**. **Unit cells** when repeated in space, a **crystal **is obtained. The concept of **unit cell** will become more. Clear if we consider a block made of equal sized bricks. If so, then each brick is a **unit cell** of this block.

Generally we can **define a unit cell** as, it is the smallest, but complete unit in space lattice which when repeated in three dimensions generates the **crystal**. A **unit cell** is the smallest building block of a **crystal**.

**A unit cell is characterized by the following parameters:**

**Edges or Edge lengths:**The intersection of two faces of**crystal lattice**is called as edge. The three edges denoted by a, b and c represents the dimension (lengths) of the unit cell along three axes. These edges may or may not be mutually perpendicular.**Angles between the edges (or planes):**There are three angles between the edges of the unit cell represented as alpha, beta and gamma.- The angle alpha is between edges b and c.
- The angle beta is between edges a and c.
- The angle gamma is between edges a and b. The cell is defined with the help of these parameters of its unit cell.

The distances a, b and c in a **unit cell** are called the unit lengths and the angles are called as axial angles. It must be remembered that the chice of **unit cell** is somewhat arbitrary, because the lattice points can be joined in more than one different ways. However, a unit cell is so chosen that it should exhibit the external geometry of the **crystals.**

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*unit cell**unit cell definition**lattice structure**crystalline structure**ionic lattice**lattices**space lattice*