Crystal Defects

In a crystalline solid, the atoms, ions, or molecules are arranged in a definite repeating pattern, but occasional defects may occur in the pattern. Several types of defects are known, as illustrated in Figure 1 . Vacancies are defects that occur when positions that should contain atoms or ions are vacant. Less commonly, some atoms or ions in a crystal may occupy positions, called interstitial sites, located between the regular positions for atoms. Other distortions are found in impure crystals, as, for example, when the cations, anions, or molecules of the impurity are too large to fit into the regular positions without distorting the structure. Trace amounts of impurities are sometimes added to a crystal (a process known as doping) in order to create defects in the structure that yield desirable changes in its properties. For example, silicon crystals are doped with varying amounts of different elements to yield suitable electrical properties for their use in the manufacture of semiconductors and computer chips.

Figure 1 : Types of crystal defects include vacancies, interstitial atoms, and substitutions impurities.

مواضيع ذات صلة

Properties of Solids

Molecular Solids

Covalent Network Solids

Metallic Solids

Ionic Solids

The Fundamental Types of Crystalline Solids

Interstitial Void Spaces

The FCC unit cell

The cubic close-packed structure

The Hexagonal closed-packed structure

Two choices for the third layer lead to two different close-packed lattice types

Close-packed lattices in three dimensions