Explain basic types of crystal structures in metal

What is crystal structure?

Definition of crystal structure:

We know that crystal structure deals with the atomic arrangement in the solid crystal structure show the regular three-dimensional pattern of atoms. In geometric terms, crystal structure is known as space lattice or point lattice. Basically, there are four types of crystal structure as follows:

Types of crystal structures:

  • Simple Cubic Crystal Structure (SC)
  • Body-Centered Crystal Structure (BCC)
  • Face Centered Crystal Structure (FCC)
  • Hexagonal close packed structure (HCP)

Basic types of crystal structures in metal
Diagram of types of crystal structures
Basic types of crystal structures in metal

1. Simple Cubic Crystal Structure (SC) :

In this type of crystal structure, one atom is situated at each corner of the unit cell as shown in the figure. In the simple cubic crystal structure, the total number of atoms is equal to eight.
Simple cubic crystal structure does not have an atom at the center of the unit cell or faces of the unit cell. Now we can say that the average number of atoms per unit in a simple cubic crystal structure one. This type of crystal structure does not exist in any engineering material.

2. Body-Centered Crystal Structure (BCC) :

In body centered crystal structure, one atom is placed at each corner of the unit cell like a simple cubic crystal structure but, in addition to this, there is one atom at the center of the unit cell. A body-centered crystal structure is more complex as compared to the simple cubic crystal structure.
Center atom in the body centered crystal structure does not come in contact with another atom, hence remains unshared. An average number of atoms per unit cell in body centered crystal structure is two. Metals like Li, K, Na, V, Ta, etc. has this type of crystal structure.

3. Face Centered Crystal Structure (FCC) :

In face-centered crystal structure, an atom is placed at each corner of the unit cell that is eight corner atoms. One atom is placed at each face center that is six face atoms. In Face centered crystal structure, there is no center atom. In this type of crystal structure, an average number of atoms per unit cell is four. Metals like Cu, Ag, Al, Ca, Pt, etc. contain this type of crystal structure.

4. Hexagonal close packed structure (HCP) :

In Hexagonal close packed structure, crystal structure shows one atom at each corner of the hexagon. Therefore, there are 12 corner atoms in the hexagonal close packed structure. Also, there is one atom on each face of the hexagon.
Interior three atoms in the hexagon remain unshared. In hexagonal close packed structure, an average number of atoms per unit cell is six. Metal like Zn, Co, Cd, Mg, Be, Ca, etc. has this type of crystal structure.

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