Tetragonal crystal system

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An example of the tetragonal crystals, wulfenite

Two different views (top down and from the side) of the unit cell of tP30-CrFe (σ-phase Frank–Kasper structure) that show its different side lengths, making this structure a member of the tetragonal crystal system.

In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square base (a by a) and height (c, which is different from a).

Bravais latticesEdit

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There are two tetragonal Bravais lattices: the primitive tetragonal and the body-centered tetragonal.

Bravais lattice	Primitive tetragonal	Body-centered tetragonal
Pearson symbol	tP	tI
Unit cell	File:Tetragonal.svg	File:Body-centered tetragonal.svg

The body-centered tetragonal lattice is equivalent to the primitive tetragonal lattice with a smaller unit cell, while the face-centered tetragonal lattice is equivalent to the body-centered tetragonal lattice with a smaller unit cell.<ref>Cubic-to-Tetragonal Transition</ref>

Crystal classesEdit

Template:Further The point groups that fall under this crystal system are listed below, followed by their representations in international notation, Schoenflies notation, orbifold notation, Coxeter notation and mineral examples.<ref>Webmineral data</ref><ref>Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., pp. 73–78, Template:Isbn </ref>

#	Point group					Type	Example	Space groups
#	citation	CitationClass=web }}</ref>	Intl	Schoen.	Orb.	Type	Example	Cox.	Primitive	Body-centered
75–80	Tetragonal pyramidal	4	C₄	44	[4]⁺	enantiomorphic polar	pinnoite, piypite	P4, P4₁, P4₂, P4₃	I4, I4₁
81–82	Tetragonal disphenoidal	Template:Overline	S₄	2×	[2⁺,4⁺]		cahnite, tugtupite	PTemplate:Overline	ITemplate:Overline
83–88	Tetragonal dipyramidal	4/m	C_4h	4*	[2,4⁺]	centrosymmetric	scheelite, wulfenite, leucite	P4/m, P4₂/m, P4/n, P4₂/n	I4/m, I4₁/a
89–98	Tetragonal trapezohedral	422	D₄	224	[2,4]⁺	enantiomorphic	cristobalite, wardite	P422, P42₁2, P4₁22, P4₁2₁2, P4₂22, P4₂2₁2, P4₃22, P4₃2₁2	I422, I4₁22
99–110	Ditetragonal pyramidal	4mm	C_4v	*44	[4]	polar	diaboleite	P4mm, P4bm, P4₂cm, P4₂nm, P4cc, P4nc, P4₂mc, P4₂bc	I4mm, I4cm, I4₁md, I4₁cd
111–122	Tetragonal scalenohedral	Template:Overline2m	D_2d (V_d)	2*2	[2⁺,4]		chalcopyrite, stannite	PTemplate:Overline2m, PTemplate:Overline2c, PTemplate:Overline2₁m, PTemplate:Overline2₁c, PTemplate:Overlinem2, PTemplate:Overlinec2, PTemplate:Overlineb2, PTemplate:Overlinen2	ITemplate:Overlinem2, ITemplate:Overlinec2, ITemplate:Overline2m, ITemplate:Overline2d
123–142	Ditetragonal dipyramidal	4/mmm	D_4h	*224	[2,4]	centrosymmetric	rutile, pyrolusite, zircon	P4/mmm, P4/mcc, P4/nbm, P4/nnc, P4/mbm, P4/mnc, P4/nmm, P4/ncc, P4₂/mmc, P4₂/mcm, P4₂/nbc, P4₂/nnm, P4₂/mbc, P4₂/mnm, P4₂/nmc, P4₂/ncm	I4/mmm, I4/mcm, I4₁/amd, I4₁/acd

In two dimensionsEdit

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} There is only one tetragonal Bravais lattice in two dimensions: the square lattice.

Bravais lattice	Square
Pearson symbol	tp
Unit cell	File:2d tp.svg

ReferencesEdit

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External linksEdit

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