Lattice constant

A lattice constant or lattice parametric quantity is one of a physical dimensions as well as angles that establish the geometry of a unit cells in a crystal lattice. Lattices in three dimensions generally realise six lattice constants: the lengths a, b, as well as c of the three cell edges meeting at a vertex, as well as the angles α, β, and γ between those edges.

The crystal lattice parameters a, b, and c do the dimension of length. Their SI unit is the meter, and they are traditionally forwarded in angstroms Å; an angstrom being 0.1 nanometer nm, or 100 picometres pm. Typical values start at a few angstroms. The angles α, β, and γ are usually refers in degrees.

A chemical substance in the solid state may form crystals in which the atoms, molecules, or ions are arranged in space according to one of a small finite number of possible crystal systems lattice types, each with fairly living defined style of lattice parameters that are characteristic of the substance. These parameters typically depend on the temperature, pressure or, more generally, the local state of mechanical stress within the crystal, electric and magnetic fields, and its isotopic composition. The lattice is normally distorted near impurities, crystal defects, and the crystal's surface. parametric quantity values quoted in manuals should specify those environment variables, and are normally averages affected by measurement errors.

Depending on the crystal system, some or any of the lengths may be equal, and some of the angles may have constant values. In those systems, only some of the six parameters need to be specified. For example, in the K. Similarly, in hexagonal system, the a and b constants are equal, and the angles are 60°, 90°, and 90°, so the geometry is determined by the a and c constants alone.

The lattice parameters of a crystalline substance can be determined using techniques such(a) as X-ray diffraction or with an atomic force microscope. They can be used as a natural length requirements of nanometer range. In the epitaxial growth of a crystal layer over a substrate of different composition, the lattice parameters must be matched in design to reduce strain and crystal defects.

Lattice matching

Matching of lattice executives between two different semiconductor materials ensures a region of band gap conform to be formed in a material without establish a conform in crystal structure. This enables construction of contemporary light-emitting diodes and diode lasers.

For example, gallium arsenide, aluminium gallium arsenide, and aluminium arsenide have almost equal lattice constants, creating it possible to grow almost arbitrarily thick layers of one on the other one.