Monoclinic crystal system

An example of the monoclinic crystals, orthoclase

In crystallography, the monoclinic crystal system is one of the 7 crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic system. They form a rectangular prism with a parallelogram as its base. Hence two vectors are perpendicular (meet at right angles), while the third vector meets the other two at an angle other than 90°.

Bravais lattices

Further information: Bravais lattice


There is only one monoclinic Bravais lattice in two dimensions: the oblique lattice.


Two monoclinic Bravais lattices exist: the primitive monoclinic and the centered monoclinic lattices.

Bravais lattice Primitive
Pearson symbol mP mS
Standard unit cell
Clinorhombic prism unit cell

In the monoclinic system there is a second choice of crystal axes that results in a unit cell with the shape of a clinorhombic prism,[1] although this axis setting is very rarely used; this is because the rectangular two-dimensional base layers can also be described with rhombic axes. In this axis setting, the primitive and base-centered lattices interchange in centering type.

Crystal classes

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

# Point group Type
Space groups
Name Schoenflies notation (Schön.) Hermann–Mauguin notation (Intl) orbifold (Orb.) Coxeter notation (Cox.)
3–5 Sphenoidal [3] C2 2 22 [2]+ enantiomorphic polar
P2, P21
6–9 Domatic [3] C1h (=C1v = Cs) 2 = m *11 [ ] polar
Pm, Pc
Cm, Cc
10–15 Prismatic [3] C2h 2/m 2* [2,2+] centrosymmetric
P2/m, P21/m, C2/m
P2/c, P21/c, C2/c

Sphenoidal is also monoclinic hemimorphic; Domatic is also monoclinic hemihedral; Prismatic is also monoclinic normal.

The three monoclinic hemimorphic space groups are as follows:

The four monoclinic hemihedral space groups include

See also


  1. See Hahn (2002), p. 746, row mC, column Primitive, where the cell parameters are given as a1 = a2, α = β
  2. Prince, E., ed. (2006). International Tables for Crystallography. International Union of Crystallography. doi:10.1107/97809553602060000001. ISBN 978-1-4020-4969-9.
  3. 1 2 3 "The 32 crystal classes". Retrieved 2009-07-08.

Further reading

This article is issued from Wikipedia - version of the 11/15/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.