The Solid State

Quickly browse through questions and notes on related topics. You can also download and read this topic offline.

• Questions
• Summary

Crystal lattice: A regular arrangement of atoms, molecules or ions in the three-dimensional space.

Only 14 three dimensional lattices are possible called as Bravais Lattices.

Characteristics of crystal lattice:

1. Each point in the lattice is called lattice point or lattice site that represents one constituent particle which may be an atom, a molecule (a group of atoms) or an ion.
2. Lattice points are joined by straight lines to bring out the geometry of the lattice.

Seven crystal structure: Cubic, Tetragonal, Orthorhombic, Monoclinic, Hexagonal, Rhombohedral, Triclinic.

Lattice sites (points): The positions which are occupied by the constituent particles in the crystal lattice.

Unit Cell: The smallest repeating portion of a crystal lattice which, when repeated in different direction generates the entire lattice.

A unit cell is characterised by six parameters such as edges: a,b,c and angles: α,β.γ.

1. Dimensions along the three edges, a,b and c. These edges may or may not be mutually perpendicular.
2. Angles between the edges, α (between b and c),β (between a and c) and γ (between a and b).

Types of Unit cells: It is broadly divided into two categories

1. Primitive
2. Centred unit cells