Crystal Structure

  Crystal Structure

• Space Lattice: lattice is a periodic arrangement of imaginary points in space.   
• Basis: Basis is an atom or group of atoms. By attaching the basis to each lattice point, we'll get a crystal structure.    

                            Lattice + Basis = Crystal structure 

• Basis of one atom is called a Monoatomic crystal.
• Basis of more than one atom is called a Polyatomic crystal.

Unit cell

The unit cell is the smallest unit cell of the crystal or lattice which on continuous reputation can generate the whole lattice. 

 

Unit cell is of two types:

• Primitive cell
• Non-Primitive cell 

(I) Primitive cell: Lattice points belonging to the corners of the unit cell. The effective number of lattice points in a primitive unit cell is one. 

(ii) Non-primitive unit cell (NP): The lattice points are belonging to the non-primitive cell lie at corners as well as the other position of the unit cell. The effective number of lattice points in a non-primitive unit cell is more than one. 

 The fourteen lattices corresponding to seven crystal systems are  known as BRAVAIS LATTICES.

Co-ordination Number: The number nearest neighbours of a particle is called coordination Number.

Packing Efficiency or Packing fraction

The ratio of the volume of all the atoms in a unit cell to the volume of a unit cell is known as packing efficiency.

 Packing Efficiency = Volume occupied by atoms present in a crystal/Volume of crystal 

Let me know if you have more questions or if there is a specific topic that you would like to know more about.