 Monoclinic crystal system

In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. They form a rectangular prism with a parallelogram as its base. Hence two pairs of vectors are perpendicular, while the third pair makes an angle other than 90°.
Contents
Bravais lattices and point/space groups
Two monoclinic Bravais lattices exist: the primitive monoclinic and the centered monoclinic lattices, with layers with a rectangular and rhombic lattice, respectively.
Monoclinic Bravais lattice Primitive (P) Basecentered (C) Crystal Classes
The monoclinic crystal system class names, examples, Schönflies notation, HermannMauguin notation, point groups, International Tables for Crystallography space group number,^{[1]} orbifold, type, and space groups are listed in the table below.
# Point group Example Type Space groups Name Schönflies Intl orbifold Coxeter 35 monoclinic ^{[2]} C_{2} 22 [2]^{+} halotrichite enantiomorphic polar 69 Domatic ^{[2]} C_{1h} (=C_{1v} = C_{s}) *11 [ ] hilgardite polar 1015 Prismatic ^{[2]} C_{2h} 2* [2,2^{+}] gypsum centrosymmetric Sphenoidal is also monoclinic hemimorphic; Domatic is also monoclinic hemihedral; Prismatic is also monoclinic normal.
The three monoclinic hemimorphic space groups are as follows:
 a prism with as crosssection wallpaper group p2
 ditto with screw axes instead of axes
 ditto with screw axes as well as axes, parallel, in between; in this case an additional translation vector is one half of a translation vector in the base plane plus one half of a perpendicular vector between the base planes
The four monoclinic hemihedral space groups include
 those with pure reflection at the base of the prism and halfway
 those with glide planes instead of pure reflection planes; the glide is one half of a translation vector in the base plane
 those with both in between each other; in this case an additional translation vector is this glide plus one half of a perpendicular vector between the base planes.
Specific chemical examples
An example of a monoclinic crystal is elemental sulfur (which can also occur in a rhombic form).^{[3]}
See also
References
 ^ Prince, E., ed (2006). International Tables for Crystallography. International Union of Crystallography. doi:10.1107/97809553602060000001. ISBN 9781402049699.
 ^ ^{a} ^{b} ^{c} "The 32 crystal classes". http://www.cartage.org.lb/en/themes/sciences/physics/SolidStatePhysics/AtomicBonding/CrystalStructure/32Crystal/32Crystal.htm. Retrieved 20090708.
 ^ C.Michael Hogan. 2011. Sulfur. Encyclopedia of Earth, eds. A.Jorgensen and C.J.Cleveland, National Council for Science and the environment, Washington DC
 Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., pp. 65 – 69, ISBN 0471805807
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