gitterparameter

Gitterparameter is a term used in crystallography to describe the geometry of a crystal’s unit cell. It comprises the lengths of the three lattice vectors, a, b and c, and the three interaxial angles, alpha, beta and gamma, which define the cell shape and size. These parameters together determine the unit cell volume and the arrangement of atoms within the crystal.

The lattice parameters are typically measured in angstroms for lengths and degrees for angles. In many materials, a, b and c, as well as alpha, beta and gamma, vary with temperature and pressure, leading to thermal expansion or compression and, in some cases, anisotropic changes where different directions expand or contract unequally. Accurate knowledge of the lattice parameters is essential for understanding crystal structure, phase transitions and material properties.

Lattice geometry depends on the crystal system. For example, in a cubic system a = b = c and alpha = beta = gamma = 90 degrees. In a tetragonal system a = b ≠ c with all angles at 90 degrees. The orthorhombic system has a ≠ b ≠ c with all angles 90 degrees. The hexagonal system has a = b ≠ c, with alpha = beta = 90 degrees and gamma = 120 degrees. Other systems include monoclinic and triclinic, which have different combinations of unequal edges and non-90-degree angles. The lattice parameters, together with the atomic basis, define the full crystal structure and are used to calculate properties such as unit cell volume and material density.

Determination of lattice parameters is commonly performed by X-ray diffraction, neutron diffraction or electron diffraction techniques.