Zellparameter

Zellparameter is a term used in crystallography to describe the lattice parameters of a crystal’s unit cell. These parameters specify the cell’s size and shape and comprise three edge lengths a, b, and c, together with three interaxial angles α, β, and γ. Collectively, they define the geometry of the repeating unit that constructs the crystal lattice. In English, the term is commonly called lattice parameters or cell parameters.

The Zellparameter are determined experimentally by diffraction techniques, such as X-ray, neutron, or electron diffraction. By analyzing the positions and intensities of diffraction peaks, researchers extract the values of a, b, c and α, β, γ for the conventional unit cell. Reported values are typically given in angstroms for lengths and degrees for angles. Depending on the material and chosen cell, a primitive cell or a conventional cell may be used, and sometimes multiple sets of parameters are reported for different crystallographic settings.

The six crystal systems are defined by constraints on Zellparameter values, such as equalities among a, b, c and right angles. For example, cubic systems have a = b = c with α = β = γ = 90°, while orthorhombic systems have a ≠ b ≠ c with all angles at 90°. The parameters determine not only the cell shape and volume but also the crystal’s density and packing efficiency. They are essential for indexing diffraction data, modeling crystal structures, and understanding phase transitions, thermal expansion, and pressure effects.

In literature, Zellparameter is used mainly in German-speaking contexts; in English, lattice parameters or cell parameters are the common terms.