orthorhombinen

Orthorhombic is one of the seven crystal systems used in crystallography to classify crystalline arrangements by their lattice geometry. It is defined by three mutually perpendicular axes of unequal length, with all interaxial angles equal to 90 degrees. In crystallographic terms, the unit cell is a rectangular parallelepiped with edge lengths a, b and c where a, b and c are all different.

In the orthorhombic system, the Bravais lattice can be primitive (P), base-centered (C), or body-centered (I). There are no face-centered lattices in this system. The symmetry of orthorhombic crystals is lower than cubic or tetragonal systems, typically featuring two-fold rotation axes and mirror planes arranged along the three perpendicular directions. The system comprises several crystal classes (point groups) that give rise to a wide range of space-group possibilities.

Orthorhombic crystals occur widely in minerals and inorganic compounds. A classical example is olivine, whose (Mg,Fe)2SiO4 structure crystallizes in the orthorhombic system. The arrangement and spacing of atoms in orthorhombic lattices influence properties such as density, hardness and diffraction patterns, making this system important in mineralogy, geology and materials science.

Determining whether a sample is orthorhombic is commonly done through techniques like X-ray diffraction and electron microscopy, which reveal the distinct perpendicular axis lengths and 90-degree angles that define the system. Etymologically, the term derives from Greek roots meaning straight and rhombus, reflecting the rectangular geometry of the unit cell.