Point Defects in Crystals: Schottky and Frenkel A point defect is a missing atom or molecule in a crystal lattice. This can be caused by a variety of fac...
A point defect is a missing atom or molecule in a crystal lattice. This can be caused by a variety of factors, including vacancies, missing atoms, or missing molecules. These point defects can have a significant impact on the properties of a crystal, including its electrical conductivity, optical absorption, and mechanical strength.
There are two main types of point defects: Schottky defects and Frenkel defects.
Schottky defects are caused by the presence of a missing atom in a regular lattice position. This can occur when an atom from a neighboring site jumps into the empty space left by the missing atom. For example, in a crystal of sodium chloride (NaCl), a sodium atom can jump into the empty space left by a chlorine atom, creating a Schottky defect.
Frenkel defects are caused by the presence of a missing molecule in a regular lattice position. This can occur when a molecule from a neighboring site jumps into the empty space left by the missing molecule. For example, in a crystal of diamond, a carbon atom can jump into the empty space left by a missing carbon molecule, creating a Frenkel defect.
The properties of a crystal with point defects can be different from the properties of a crystal without point defects. For example, a crystal with point defects may be more electrically conductive than a crystal without point defects, as the point defects can provide additional pathways for electrons to flow. A crystal with point defects may also be more prone to defects and degradation, as the point defects can provide sites for defects to form