Orthorhombic crystal system

In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base (a by b) and height (c), such that a, b, and c are distinct. All three bases intersect at 90° angles, so the three lattice vectors remain mutually orthogonal.

Bravais lattices

There are four orthorhombic Bravais lattices: primitive orthorhombic, base-centered orthorhombic, body-centered orthorhombic, and face-centered orthorhombic.

Bravais latticePrimitive
orthorhombic
Base-centered
orthorhombic
Body-centered
orthorhombic
Face-centered
orthorhombic
Pearson symboloPoSoIoF
Unit cell

For the base-centered orthorhombic lattice, the primitive cell has the shape of a right rhombic prism;[1] it can be constructed because the two-dimensional centered rectangular base layer can also be described with primitive rhombic axes. Note that the length of the primitive cell below equals of the conventional cell above.

Right rhombic prism primitive cell
Primitive cell of the base-centered orthorhombic lattice
Relationship between base layers of primitive and conventional cells

Crystal classes

The orthorhombic crystal system class names, examples, Schönflies notation, Hermann-Mauguin notation, point groups, International Tables for Crystallography space group number,[2] orbifold notation, type, and space groups are listed in the table below.

Point groupTypeExampleSpace groups
Name[3]Schön.IntlOrb.Cox. PrimitiveBase-centeredFace-centeredBody-centered
16–24Rhombic disphenoidalD2 (V)222222[2,2]+EnantiomorphicEpsomiteP222, P2221, P21212, P212121C2221, C222F222I222, I212121
25–46Rhombic pyramidalC2vmm2*22[2]PolarHemimorphite, bertranditePmm2, Pmc21, Pcc2, Pma2, Pca21, Pnc2, Pmn21, Pba2, Pna21, Pnn2Cmm2, Cmc21, Ccc2
Amm2, Aem2, Ama2, Aea2
Fmm2, Fdd2Imm2, Iba2, Ima2
47–74Rhombic dipyramidalD2h (Vh)mmm*222[2,2]CentrosymmetricOlivine, aragonite, marcasitePmmm, Pnnn, Pccm, Pban, Pmma, Pnna, Pmna, Pcca, Pbam, Pccn, Pbcm, Pnnm, Pmmn, Pbcn, Pbca, PnmaCmcm, Cmca, Cmmm, Cccm, Cmme, CcceFmmm, FdddImmm, Ibam, Ibca, Imma

In two dimensions

In two dimensions there are two orthorhombic Bravais lattices: primitive rectangular and centered rectangular.

Bravais latticeRectangularCentered rectangular
Pearson symbolopoc
Unit cell

See also

References

Further reading