:Allotropy

{{short description|Property of some chemical elements to exist in two or more different forms}}

{{distinguish|Xenophagy{{!}}Allotrophy}}

File:Diamond and graphite.jpg and graphite are two allotropes of carbon: pure forms of the same element that differ in crystalline structure.]]

Allotropy or allotropism ({{ety|grc|ἄλλος (allos)|other||τρόπος (tropos)|manner, form}}) is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element: the atoms of the element are bonded together in different manners.{{GoldBookRef|title=Allotrope|file=A00243|accessdate=August 11, 2015}}

For example, the allotropes of carbon include diamond (the carbon atoms are bonded together to form a cubic lattice of tetrahedra), graphite (the carbon atoms are bonded together in sheets of a hexagonal lattice), graphene (single sheets of graphite), and fullerenes (the carbon atoms are bonded together in spherical, tubular, or ellipsoidal formations).

The term allotropy is used for elements only, not for compounds. The more general term, used for any compound, is polymorphism, although its use is usually restricted to solid materials such as crystals. Allotropy refers only to different forms of an element within the same physical phase (the state of matter, such as a solid, liquid or gas). The differences between these states of matter would not alone constitute examples of allotropy. Allotropes of chemical elements are frequently referred to as polymorphs or as phases of the element.

For some elements, allotropes have different molecular formulae or different crystalline structures, as well as a difference in physical phase; for example, two allotropes of oxygen (dioxygen, O₂, and ozone, O₃) can both exist in the solid, liquid and gaseous states. Other elements do not maintain distinct allotropes in different physical phases; for example, phosphorus has numerous solid allotropes, which all revert to the same P₄ form when melted to the liquid state.

History

The concept of allotropy was originally proposed in 1840 by the Swedish scientist Baron Jöns Jakob Berzelius (1779–1848).See:

{{cite book |last1=Berzelius |first1=Jac. |title=Årsberättelse om Framstegen i Fysik och Kemi afgifven den 31 Mars 1840. Första delen. |trans-title=Annual Report on Progress in Physics and Chemistry submitted March 31, 1840. First part. |date=1841 |publisher=P.A. Norstedt & Söner |location=Stockholm, Sweden |page=14 |url=https://babel.hathitrust.org/cgi/pt?id=nyp.33433009789326&view=1up&seq=176 |language=Swedish}} From p. 14: "Om det ock passar väl för att uttrycka förhållandet emellan myrsyrad ethyloxid och ättiksyrad methyloxid, så är det icke passande för de olika tillstånd hos de enkla kropparne, hvari dessa blifva af skiljaktiga egenskaper, och torde för dem böra ersättas af en bättre vald benämning, t. ex. Allotropi (af αλλότροπος, som betyder: af olika beskaffenhet) eller allotropiskt tillstånd." (If it [i.e., the word isomer] is also well suited to express the relation between formic acid ethyl oxide [i.e., ethyl formate] and acetic acid methyloxide [i.e., methyl acetate], then it [i.e., the word isomers] is not suitable for different conditions of simple substances, where these [substances] transform to have different properties, and [therefore the word isomers] should be replaced, in their case, by a better chosen name; for example, Allotropy (from αλλότροπος, which means: of different nature) or allotropic condition.)
Republished in German: {{cite journal |last1=Berzelius |first1=Jacob |last2=Wöhler |first2=F. |title=Jahres-Bericht über die Fortschritte der physischen Wissenschaften |journal=Jahres Bericht Über die Fortschritte der Physischen Wissenschaften |trans-title= Annual Report on Progress of the Physical Sciences |date=1841 |publisher=Laupp'schen Buchhandlung |location=Tübingen, (Germany) |volume= 20 |page=13 |url=https://babel.hathitrust.org/cgi/pt?id=umn.31951d000120766&view=1up&seq=189 |language=German}} From p. 13: "Wenn es sich auch noch gut eignet, um das Verhältniss zwischen ameisensaurem Äthyloxyd und essigsaurem Methyloxyd auszudrücken, so ist es nicht passend für ungleiche Zustände bei Körpern, in welchen diese verschiedene Eigenschaften annehmen, und dürfte für diese durch eine besser gewählte Benennung zu ersetzen sein, z. B. durch Allotropie (von αλλότροπος, welches bedeutet: von ungleicher Beschaffenheit), oder durch allotropischen Zustand." (Even if it [i.e., the word isomer] is still well suited to express the relation between ethyl formate and methyl acetate, then it is not appropriate for the distinct conditions in the case of substances where these [substances] assume different properties, and for these, [the word isomer] may be replaced with a better chosen designation, e.g., with Allotropy (from αλλότροπος, which means: of distinct character), or with allotropic condition.)
Merriam-Webster online dictionary: [https://www.merriam-webster.com/dictionary/allotropy Allotropy]{{citation | last = Jensen | first = W. B. |author1-link=William B. Jensen | title = The Origin of the Term Allotrope | journal = J. Chem. Educ. | year = 2006 | volume = 83 | issue = 6 | pages = 838–39 | doi = 10.1021/ed083p838|bibcode = 2006JChEd..83..838J }}. The term is derived {{ety|gre|άλλοτροπἱα (allotropia)|variability, changeableness}}.{{Citation | contribution = allotropy | title = A New English Dictionary on Historical Principles | volume = 1 | publisher = Oxford University Press | year = 1888 | page = 238}}. After the acceptance of Avogadro's hypothesis in 1860, it was understood that elements could exist as polyatomic molecules, and two allotropes of oxygen were recognized as O₂ and O₃. In the early 20th century, it was recognized that other cases such as carbon were due to differences in crystal structure.

By 1912, Ostwald noted that the allotropy of elements is just a special case of the phenomenon of polymorphism known for compounds, and proposed that the terms allotrope and allotropy be abandoned and replaced by polymorph and polymorphism.{{cite book |last1=Ostwald |first1=Wilhelm |last2=Taylor |first2=W.W. |title=Outlines of General Chemistry |date=1912 |publisher=Macmillan and Co., Ltd. |location=London, England |page=104 |edition=3rd |url=https://books.google.com/books?id=1w1DAAAAIAAJ&pg=PA104}} From p. 104: "Substances are known which exist not only in two, but even in three, four or five different solid forms; no limitation to the number is known to exist. Such substances are called polymorphous. The name allotropy is commonly employed in the same connexion, especially when the substance is an element. There is no real reason for making this distinction, and it is preferable to allow the second less common name to die out." Although many other chemists have repeated this advice, IUPAC and most chemistry texts still favour the usage of allotrope and allotropy for elements only.Jensen 2006, citing Addison, W. E. The Allotropy of the Elements (Elsevier 1964) that many have repeated this advice.

Differences in properties of an element's allotropes

Allotropes are different structural forms of the same element and can exhibit quite different physical properties and chemical behaviours. The change between allotropic forms is triggered by the same forces that affect other structures, i.e., pressure, light, and temperature. Therefore, the stability of the particular allotropes depends on particular conditions. For instance, iron changes from a body-centered cubic structure (ferrite) to a face-centered cubic structure (austenite) above 906 °C, and tin undergoes a modification known as tin pest from a metallic form to a semimetallic form below 13.2 °C (55.8 °F). As an example of allotropes having different chemical behaviour, ozone (O₃) is a much stronger oxidizing agent than dioxygen (O₂).

List of allotropes

Typically, elements capable of variable coordination number and/or oxidation states tend to exhibit greater numbers of allotropic forms. Another contributing factor is the ability of an element to catenate.

Examples of allotropes include:

=Non-metals=

class="wikitable"
Element ! Allotropes
Carbon \| Diamond – an extremely hard, transparent crystal, with the carbon atoms arranged in a tetrahedral lattice. A poor electrical conductor. An excellent thermal conductor. Lonsdaleite – also called hexagonal diamond. Graphene – is the basic structural element of other allotropes, nanotubes, charcoal, and fullerenes. Q-carbon – a ferromagnetic, tough, and brilliant crystal structure that is harder and brighter than diamonds.{{dubious\|date=February 2019}} Graphite – a semimetallic, soft, black, flaky solid, a good electrical conductor. The C atoms are bonded in flat hexagonal lattices (graphene), which are then layered in sheets. Linear acetylenic carbon (carbyne) Amorphous carbon Fullerenes, including buckminsterfullerene, also known as "buckyballs", such as C₆₀. Carbon nanotubes – allotropes having a cylindrical nanostructure. Schwarzites Cyclocarbon Glassy carbon Superdense carbon allotropes – proposed allotropes
Nitrogen \| Dinitrogen – by far the most common and stable form of nitrogen, found in the air. Hexazine Octaazacubane Tetranitrogen Trinitrogen Solid nitrogen
Phosphorus \| White phosphorus – crystalline solid of tetraphosphorus (P₄) molecules Red phosphorus – amorphous polymeric solid Scarlet phosphorus Violet phosphorus with monoclinic crystalline structure Black phosphorus – semiconductor, analogous to graphite Diphosphorus – gaseous form composed of P₂ molecules, stable between 1200 °C and 2000 °C; created e.g. by dissociation of P₄ molecules of white phosphorus at around 827 °C
Oxygen \| Dioxygen, O₂ – colorless (faint blue liquid and solid) Ozone, O₃ – blue Tetraoxygen, O₄ – metastable Octaoxygen, O₈ – red
Sulfur \| Cyclo-Pentasulfur, Cyclo-S₅ Cyclo-Hexasulfur, Cyclo-S₆ Cyclo-Heptasulfur, Cyclo-S₇ Cyclo-Octasulfur, Cyclo-S₈
Selenium \| "Red selenium", cyclo-Se₈ Gray selenium, polymeric Se Black selenium, irregular polymeric rings up to 1000 atoms long Monoclinic selenium, dark red transparent crystals
Spin isomers of hydrogen \| Orthohydrogen, H₂ with nuclear spins aligned parallel Parahydrogen, H₂ with nuclear spins aligned antiparallel These nuclear spin isomers have sometimes been described as allotropes, notably by the committee which awarded the 1932 Nobel prize to Werner Heisenberg for quantum mechanics and singled out the "allotropic forms of hydrogen" as its most notable application.[https://www.nobelprize.org/nobel_prizes/physics/laureates/1932/heisenberg-facts.html Werner Heisenberg – Facts] Nobelprize.org

class="wikitable"

Element

! Allotropes

Carbon

Diamond – an extremely hard, transparent crystal, with the carbon atoms arranged in a tetrahedral lattice. A poor electrical conductor. An excellent thermal conductor.
Lonsdaleite – also called hexagonal diamond.
Graphene – is the basic structural element of other allotropes, nanotubes, charcoal, and fullerenes.
Q-carbon – a ferromagnetic, tough, and brilliant crystal structure that is harder and brighter than diamonds.{{dubious|date=February 2019}}
Graphite – a semimetallic, soft, black, flaky solid, a good electrical conductor. The C atoms are bonded in flat hexagonal lattices (graphene), which are then layered in sheets.
Linear acetylenic carbon (carbyne)
Amorphous carbon
Fullerenes, including buckminsterfullerene, also known as "buckyballs", such as C₆₀.
Carbon nanotubes – allotropes having a cylindrical nanostructure.
Schwarzites
Cyclocarbon
Glassy carbon
Superdense carbon allotropes – proposed allotropes

Nitrogen

Dinitrogen – by far the most common and stable form of nitrogen, found in the air.
Hexazine
Octaazacubane
Tetranitrogen
Trinitrogen
Solid nitrogen

Phosphorus

White phosphorus – crystalline solid of tetraphosphorus (P₄) molecules
Red phosphorus – amorphous polymeric solid
Scarlet phosphorus
Violet phosphorus with monoclinic crystalline structure
Black phosphorus – semiconductor, analogous to graphite
Diphosphorus – gaseous form composed of P₂ molecules, stable between 1200 °C and 2000 °C; created e.g. by dissociation of P₄ molecules of white phosphorus at around 827 °C

Oxygen

Dioxygen, O₂ – colorless (faint blue liquid and solid)
Ozone, O₃ – blue
Tetraoxygen, O₄ – metastable
Octaoxygen, O₈ – red

Sulfur

Cyclo-Pentasulfur, Cyclo-S₅
Cyclo-Hexasulfur, Cyclo-S₆
Cyclo-Heptasulfur, Cyclo-S₇
Cyclo-Octasulfur, Cyclo-S₈

Selenium

"Red selenium", cyclo-Se₈
Gray selenium, polymeric Se
Black selenium, irregular polymeric rings up to 1000 atoms long
Monoclinic selenium, dark red transparent crystals

Spin isomers of hydrogen

Orthohydrogen, H₂ with nuclear spins aligned parallel
Parahydrogen, H₂ with nuclear spins aligned antiparallel

These nuclear spin isomers have sometimes been described as allotropes, notably by the committee which awarded the 1932 Nobel prize to Werner Heisenberg for quantum mechanics and singled out the "allotropic forms of hydrogen" as its most notable application.[https://www.nobelprize.org/nobel_prizes/physics/laureates/1932/heisenberg-facts.html Werner Heisenberg – Facts] Nobelprize.org

=Metalloids=

class="wikitable"
Element ! Allotropes
Boron \| Amorphous boron – brown powder – B₁₂ regular icosahedra α-rhombohedral boron β-rhombohedral boron γ-orthorhombic boron α-tetragonal boron β-tetragonal boron High-pressure superconducting phase
Silicon \| Amorphous silicon α-silicon, a semiconductor, diamond cubic structure β-silicon - metallic, with the BCC similar to molybdenum and beta-tin (High Pressure Phase) Q-Silicon - a ferromagnetic (Similar to Q-Carbon) and highly conductive phase of silicon (similar to graphite) {{Cite web\|url=https://newatlas.com/materials/q-silicon-magnetic-spintronic-quantum-computers/\|title=Meet Q-silicon, a new magnetic material for spintronic quantum computers\|date=July 4, 2023\|website=New Atlas}} Silicene, buckled planar single layer Silicon, similar to Graphene
Germanium \| Amorphous germanium α-germanium – semimetallic element or semiconductor, with the same structure as diamond (similar chemical properties with sulfur and silicon) β-germanium – metallic, with the same structure as beta-tin Germanene – Buckled planar Germanium, similar to graphene
Arsenic \| Yellow arsenic – molecular non-metallic As₄, with the same structure as white phosphorus (Similar chemical properties with nitrogen and phosphorus) Gray arsenic, polymeric As (metallic, though heavily anisotropic) (similar to aluminum and antimony in chemical properties) Black arsenic – molecular and non-metallic, with the same structure as red phosphorus
Antimony \| Blue-white antimony – stable form (metallic), with the same structure as gray arsenic (similar to arsenic in chemical properties) Black antimony (non-metallic and amorphous, only stable as a thin layer)
Tellurium \| Amorphous tellurium – gray-black or brown powder{{cite book\|title=Advanced Inorganic Chemistry Vol-1\|author=Raj, G.\|publisher=Krishna Prakashan\|isbn=9788187224037\|url=https://books.google.com/books?id=0uwDTrxyaB8C&pg=PA1327\|page=1327\|access-date=January 6, 2017}} Crystalline tellurium – hexagonal crystalline structure (metalloid) (similar chemical properties with selenium)

class="wikitable"

Element

! Allotropes

Boron

Amorphous boron – brown powder – B₁₂ regular icosahedra
α-rhombohedral boron
β-rhombohedral boron
γ-orthorhombic boron
α-tetragonal boron
β-tetragonal boron
High-pressure superconducting phase

Silicon

Amorphous silicon
α-silicon, a semiconductor, diamond cubic structure
β-silicon - metallic, with the BCC similar to molybdenum and beta-tin (High Pressure Phase)
Q-Silicon - a ferromagnetic (Similar to Q-Carbon) and highly conductive phase of silicon (similar to graphite) {{Cite web|url=https://newatlas.com/materials/q-silicon-magnetic-spintronic-quantum-computers/|title=Meet Q-silicon, a new magnetic material for spintronic quantum computers|date=July 4, 2023|website=New Atlas}}
Silicene, buckled planar single layer Silicon, similar to Graphene

Germanium

Amorphous germanium
α-germanium – semimetallic element or semiconductor, with the same structure as diamond (similar chemical properties with sulfur and silicon)
β-germanium – metallic, with the same structure as beta-tin
Germanene – Buckled planar Germanium, similar to graphene

Arsenic

Yellow arsenic – molecular non-metallic As₄, with the same structure as white phosphorus (Similar chemical properties with nitrogen and phosphorus)
Gray arsenic, polymeric As (metallic, though heavily anisotropic) (similar to aluminum and antimony in chemical properties)
Black arsenic – molecular and non-metallic, with the same structure as red phosphorus

Antimony

Blue-white antimony – stable form (metallic), with the same structure as gray arsenic (similar to arsenic in chemical properties)
Black antimony (non-metallic and amorphous, only stable as a thin layer)

Tellurium

Amorphous tellurium – gray-black or brown powder{{cite book|title=Advanced Inorganic Chemistry Vol-1|author=Raj, G.|publisher=Krishna Prakashan|isbn=9788187224037|url=https://books.google.com/books?id=0uwDTrxyaB8C&pg=PA1327|page=1327|access-date=January 6, 2017}}
Crystalline tellurium – hexagonal crystalline structure (metalloid) (similar chemical properties with selenium)

=Metals=

Among the metallic elements that occur in nature in significant quantities (56 up to U, without Tc and Pm), almost half (27) are allotropic at ambient pressure: Li, Be, Na, Ca, Ti, Mn, Fe, Co, Sr, Y, Zr, Sn, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Yb, Hf, Tl, Th, Pa and U. Some phase transitions between allotropic forms of technologically relevant metals are those of Ti at 882 °C, Fe at 912 °C and 1,394 °C, Co at 422 °C, Zr at 863 °C, Sn at 13 °C and U at 668 °C and 776 °C.

class="wikitable"
Element !Phase name(s) !Space group !Pearson symbol !Structure type !Description
rowspan="8" \|Lithium \|style="background:lightblue;\|α-Li \|style="background:lightblue;\|R{{overline\|3}}m \|style="background:lightblue;\|hR9 \|style="background:lightblue;\|α-Sm \|style="background:lightblue;\|Forms below 70 K.{{cite journal \| last=Overhauser \| first=A. W. \| title=Crystal Structure of Lithium at 4.2 K \| journal=Physical Review Letters \| publisher=American Physical Society (APS) \| volume=53 \| issue=1 \| date=1984-07-02 \| issn=0031-9007 \| doi=10.1103/physrevlett.53.64 \| pages=64–65\| bibcode=1984PhRvL..53...64O }}
style="background:lightgreen; \|β-Li \|Im{{overline\|3}}m \|cI2 \|W \|Stable at room temperature and pressure.
style="background:lightyellow;\| \| \|Fm{{overline\|3}}m \|cF4 \|Cu \|Forms above 7GPa
style="background:lightyellow;\| \| \|R{{overline\|3}}m \|hR1 \|α-Hg \|An intermediate phase formed ~40GPa.
style="background:lightyellow;\| \| \|I{{overline\|4}}3d \|cI16 \| \|Forms above 40GPa.{{cite journal \| last1=Hanfland \| first1=M. \| last2=Syassen \| first2=K. \| last3=Christensen \| first3=N. E. \| last4=Novikov \| first4=D. L. \| title=New high-pressure phases of lithium \| journal=Nature \| publisher=Springer Science and Business Media LLC \| volume=408 \| issue=6809 \| year=2000 \| issn=0028-0836 \| doi=10.1038/35041515 \| pages=174–178\| pmid=11089965 \| bibcode=2000Natur.408..174H \| s2cid=4303422 }}
style="background:lightyellow;\| \| \| \|oC88 \| \|Forms between 60 and 70 GPa.{{cite journal \| last=Degtyareva \| first=V.F. \| title=Potassium under pressure: Electronic origin of complex structures \| journal=Solid State Sciences \| volume=36 \| date=2014 \| doi=10.1016/j.solidstatesciences.2014.07.008 \| pages=62–72\| arxiv=1310.4718 \| bibcode=2014SSSci..36...62D }}
style="background:lightyellow;\| \| \| \|oC40 \| \|Forms between 70 and 95 GPa.
style="background:lightyellow;\| \| \| \|oC24 \| \|Forms above 95 GPa.
rowspan="2"\|Beryllium \| style="background:lightgreen;\|α-Be \|style="background:lightgreen;\|P6₃/mmc \|style="background:lightgreen;\|hP2 \|style="background:lightgreen;\|Mg \|style="background:lightgreen;\|Stable at room temperature and pressure.
style="background:pink;\| \|β-Be \|Im{{overline\|3}}m \|cI2 \|W \|Forms above 1255 °C.
rowspan="7"\|Sodium \|style="background:lightblue;\|α-Na \|style="background:lightblue;\|R{{overline\|3}}m \|style="background:lightblue;\|hR9 \|style="background:lightblue;\|α-Sm \|style="background:lightblue;\|Forms below 20 K.
style="background:lightgreen;\| \|β-Na \|Im{{overline\|3}}m \|cI2 \|W \|Stable at room temperature and pressure.
style="background:lightyellow;\| \| \|Fm{{overline\|3}}m \|cF4 \|Cu \|Forms at room temperature above 65 GPa.{{cite journal \| last1=Hanfland \| first1=M. \| last2=Loa \| first2=I. \| last3=Syassen \| first3=K. \| title=Sodium under pressure: bcc to fcc structural transition and pressure-volume relation to 100 GPa \| journal=Physical Review B \| publisher=American Physical Society (APS) \| volume=65 \| issue=18 \| date=2002-05-13 \| issn=0163-1829 \| doi=10.1103/physrevb.65.184109 \| page=184109\| bibcode=2002PhRvB..65r4109H }}
style="background:lightyellow;\| \| \|I{{overline\|4}}3d \|cI16 \| \|Forms at room temperature, 108GPa.{{cite journal \| last1=McMahon \| first1=M. I. \| last2=Gregoryanz \| first2=E. \| last3=Lundegaard \| first3=L. F. \| last4=Loa \| first4=I. \| last5=Guillaume \| first5=C. \| last6=Nelmes \| first6=R. J. \| last7=Kleppe \| first7=A. K. \| last8=Amboage \| first8=M. \| last9=Wilhelm \| first9=H. \| last10=Jephcoat \| first10=A. P. \| title=Structure of sodium above 100 GPa by single-crystal x-ray diffraction \| journal=Proceedings of the National Academy of Sciences \| volume=104 \| issue=44 \| date=2007-10-18 \| issn=0027-8424 \| doi=10.1073/pnas.0709309104 \| pages=17297–17299\| pmid=17947379 \| pmc=2077250 \| bibcode=2007PNAS..10417297M \|doi-access=free}}
style="background:lightyellow;\| \| \|Pnma \|oP8 \|MnP \|Forms at room temperature, 119GPa.{{cite journal \| last1=Gregoryanz \| first1=E. \| last2=Lundegaard \| first2=L. F. \| last3=McMahon \| first3=M. I. \| last4=Guillaume \| first4=C. \| last5=Nelmes \| first5=R. J. \| last6=Mezouar \| first6=M. \| title=Structural Diversity of Sodium \| journal=Science \| publisher=American Association for the Advancement of Science (AAAS) \| volume=320 \| issue=5879 \| date=2008-05-23 \| issn=0036-8075 \| doi=10.1126/science.1155715 \| pages=1054–1057\| pmid=18497293 \| bibcode=2008Sci...320.1054G \| s2cid=29596632 }}
style="background:lightyellow;\| \| \| \|tI19* \| \|A host-guest structure that forms above between 125 and 180 GPa.
style="background:lightyellow;\| \| \| \|hP4 \| \|Forms above 180 GPa.
rowspan="2"\|Magnesium \|style="background:lightgreen;\| \|style="background:lightgreen;\|P6₃/mmc \|style="background:lightgreen;\|hP2 \|style="background:lightgreen;\|Mg \|style="background:lightgreen;\|Stable at room temperature and pressure.
style="background:lightyellow;\| \| \|Im{{overline\|3}}m \|cI2 \|W \|Forms above 50 GPa.{{cite journal \| last1=Olijnyk \| first1=H. \| last2=Holzapfel \| first2=W. B. \| title=High-pressure structural phase transition in Mg \| journal=Physical Review B \| publisher=American Physical Society (APS) \| volume=31 \| issue=7 \| date=1985-04-01 \| issn=0163-1829 \| doi=10.1103/physrevb.31.4682 \| pages=4682–4683\| pmid=9936412 \| bibcode=1985PhRvB..31.4682O }}
rowspan="2"\|Aluminium \|style="background:lightgreen;\|α-Al \|style="background:lightgreen;\|Fm{{overline\|3}}m \|style="background:lightgreen;\|cF4 \|style="background:lightgreen;\|Cu \|style="background:lightgreen;\|Stable at room temperature and pressure.
style="background:lightyellow;\| \|β-Al \|P6₃/mmc \|hP2 \|Mg \|Forms above 20.5 GPa.
rowspan="7" \|Potassium \|style="background:lightgreen;\| \|style="background:lightgreen;\|Im{{overline\|3}}m \|style="background:lightgreen;\|cI2 \|style="background:lightgreen;\|W \|style="background:lightgreen;\|Stable at room temperature and pressure.
style="background:lightyellow;\| \| \|Fm{{overline\|3}}m \|cF4 \|Cu \|Forms above 11.7 GPa.
style="background:lightyellow;\| \| \|I4/mcm \|tI19* \| \|A host-guest structure that forms at about 20 GPa.
style="background:lightyellow;\| \| \|P6₃/mmc \|hP4 \|NiAs \|Forms above 25 GPa.
style="background:lightyellow;\| \| \|Pnma \|oP8 \|MnP \|Forms above 58GPa.
style="background:lightyellow;\| \| \|I4₁/amd \|tI4 \| \|Forms above 112 GPa.
style="background:lightyellow;\| \| \|Cmca \|oC16 \| \|Formas above 112 GPa.
rowspan="4" \|Iron \|style="background:lightgreen;\|α-Fe, ferrite \|style="background:lightgreen;\|Im{{overline\|3}}m \|style="background:lightgreen;\|cI2 \|style="background:lightgreen;\|Body-centered cubic \|style="background:lightgreen;\|Stable at room temperature and pressure. Ferromagnetic at T<770 °C, paramagnetic from T=770–912 °C.
style="background:pink;\| \|γ-iron, austenite \|Fm{{overline\|3}}m \|cF4 \|Face-centered cubic \|Stable from 912 to 1,394 °C.
style="background:pink;\| \| δ-iron \|Im{{overline\|3}}m \|cI2 \|Body-centered cubic \|Stable from 1,394 – 1,538 °C, same structure as α-Fe.
style="background:lightyellow;\| \|ε-iron, Hexaferrum \|P6₃/mmc \|hP2 \|Hexagonal close-packed \|Stable at high pressures.
rowspan="3" \|Cobalt{{cite journal \|last1=de la Peña O’Shea \|first1=Víctor Antonio \|last2=Moreira \|first2=Iberio de P. R. \|last3=Roldán \|first3=Alberto \|last4=Illas \|first4=Francesc \|title=Electronic and magnetic structure of bulk cobalt: The α, β, and ε-phases from density functional theory calculations \|journal=The Journal of Chemical Physics \|date=8 July 2010 \|volume=133 \|issue=2 \|page=024701 \|doi=10.1063/1.3458691 \|pmid=20632764 }} \|style="background:lightgreen;\|α-Cobalt \|style="background:lightgreen;\| \|style="background:lightgreen;\| \|style="background:lightgreen;\|hexagonal-close packed \|style="background:lightgreen;\|Forms below 450 °C.
style="background:pink;\| \|β-Cobalt \| \| \|face centered cubic \|Forms above 450 °C.
style="background:lightyellow;\| \|ε-Cobalt \|P4₁32 \| \|primitive cubic \|Forms from thermal decomposition of [Co₂CO₈]. Nanoallotrope.
rowspan="6"\|Rubidium \|style="background:lightgreen;\|α-Rb \|style="background:lightgreen;\|Im{{overline\|3}}m \|style="background:lightgreen;\|cI2 \|style="background:lightgreen;\|W \|style="background:lightgreen;\|Stable at room temperature and pressure.
style="background:lightyellow;\| \| \| \|cF4 \| \|Forms above 7 GPa.
style="background:lightyellow;\| \| \| \|oC52 \| \|Forms above 13 GPa.
style="background:lightyellow;\| \| \| \|tI19* \| \|Forms above 17 GPa.
style="background:lightyellow;\| \| \| \|tI4 \| \|Forms above 20 GPa.
style="background:lightyellow;\| \| \| \|oC16 \| \|Forms above 48 GPa.
rowspan="7" \|Tin \|style="background:lightblue;\|α-tin, gray tin, tin pest \|style="background:lightblue;\|Fd{{overline\|3}}m \|style="background:lightblue;\|cF8 \|style="background:lightblue;\|d-C \|style="background:lightblue;\|Stable below 13.2 °C.
style="background:lightgreen;\| \|β-tin, white tin \|I4₁/amd \|tI4 \|β-Sn \|Stable at room temperature and pressure.
style="background:lightyellow;\| \|γ-tin, rhombic tin \|I4/mmm \|tI2 \|In \|Forms above 10 GPa.{{cite journal \| last1=Deffrennes \| first1=Guillaume \| last2=Faure \| first2=Philippe \| last3=Bottin \| first3=François \| last4=Joubert \| first4=Jean-Marc \| last5=Oudot \| first5=Benoit \| title=Tin (Sn) at high pressure: Review, X-ray diffraction, DFT calculations, and Gibbs energy modeling \| journal=Journal of Alloys and Compounds \| volume=919 \| date=2022 \| doi=10.1016/j.jallcom.2022.165675 \| page=165675\|arxiv=2203.16240}}
style="background:lightyellow;\| \|γ'-Sn \|Immm \|oI2 \|MoPt₂ \|Forms above 30 GPa.
style="background:lightyellow;\| \|σ-Sn, γ"-Sn \|Im{{overline\|3}}m \|cI2 \|W \|Forms above 41 GPa. Forms at very high pressure.{{cite journal\|first = A. M.\|last = Molodets\|author2=Nabatov, S. S.\|title = Thermodynamic Potentials, Diagram of State, and Phase Transitions of Tin on Shock Compression\|journal = High Temperature\|volume = 38\|issue = 5\|year = 2000\|pages = 715–721\|doi = 10.1007/BF02755923\| bibcode=2000HTemp..38..715M \|s2cid = 120417927}}
style="background:lightyellow;\| \|δ-Sn \|P6₃/mmc \|hP2 \|Mg \|Forms above 157 GPa.
Stanene \| \| \|
rowspan="2" \|Polonium \|style="background:lightgreen;\|α-Polonium \|style="background:lightgreen;\| \|style="background:lightgreen;\| \|style="background:lightgreen;\|simple cubic \|style="background:lightgreen;\|
β-Polonium \| \| \|rhombohedral \|

class="wikitable"

Element

!Phase name(s)

!Space group

!Pearson symbol

!Structure type

!Description

rowspan="8" |Lithium

|style="background:lightblue;|α-Li

|style="background:lightblue;|R{{overline|3}}m

|style="background:lightblue;|hR9

|style="background:lightblue;|α-Sm

|style="background:lightblue;|Forms below 70 K.{{cite journal | last=Overhauser | first=A. W. | title=Crystal Structure of Lithium at 4.2 K | journal=Physical Review Letters | publisher=American Physical Society (APS) | volume=53 | issue=1 | date=1984-07-02 | issn=0031-9007 | doi=10.1103/physrevlett.53.64 | pages=64–65| bibcode=1984PhRvL..53...64O }}

style="background:lightgreen;

|β-Li

|Im{{overline|3}}m

|cI2

|Stable at room temperature and pressure.

style="background:lightyellow;|

|Fm{{overline|3}}m

|cF4

|Cu

|Forms above 7GPa

style="background:lightyellow;|

|R{{overline|3}}m

|hR1

|α-Hg

|An intermediate phase formed ~40GPa.

style="background:lightyellow;|

|I{{overline|4}}3d

|cI16

|Forms above 40GPa.{{cite journal | last1=Hanfland | first1=M. | last2=Syassen | first2=K. | last3=Christensen | first3=N. E. | last4=Novikov | first4=D. L. | title=New high-pressure phases of lithium | journal=Nature | publisher=Springer Science and Business Media LLC | volume=408 | issue=6809 | year=2000 | issn=0028-0836 | doi=10.1038/35041515 | pages=174–178| pmid=11089965 | bibcode=2000Natur.408..174H | s2cid=4303422 }}

style="background:lightyellow;|

|oC88

|Forms between 60 and 70 GPa.{{cite journal | last=Degtyareva | first=V.F. | title=Potassium under pressure: Electronic origin of complex structures | journal=Solid State Sciences | volume=36 | date=2014 | doi=10.1016/j.solidstatesciences.2014.07.008 | pages=62–72| arxiv=1310.4718 | bibcode=2014SSSci..36...62D }}

style="background:lightyellow;|

|oC40

|Forms between 70 and 95 GPa.

style="background:lightyellow;|

|oC24

|Forms above 95 GPa.

rowspan="2"|Beryllium

| style="background:lightgreen;|α-Be

|style="background:lightgreen;|P6₃/mmc

|style="background:lightgreen;|hP2

|style="background:lightgreen;|Mg

|style="background:lightgreen;|Stable at room temperature and pressure.

style="background:pink;|

|β-Be

|Im{{overline|3}}m

|cI2

|Forms above 1255 °C.

rowspan="7"|Sodium

|style="background:lightblue;|α-Na

|style="background:lightblue;|R{{overline|3}}m

|style="background:lightblue;|hR9

|style="background:lightblue;|α-Sm

|style="background:lightblue;|Forms below 20 K.

style="background:lightgreen;|

|β-Na

|Im{{overline|3}}m

|cI2

|Stable at room temperature and pressure.

style="background:lightyellow;|

|Fm{{overline|3}}m

|cF4

|Cu

|Forms at room temperature above 65 GPa.{{cite journal | last1=Hanfland | first1=M. | last2=Loa | first2=I. | last3=Syassen | first3=K. | title=Sodium under pressure: bcc to fcc structural transition and pressure-volume relation to 100 GPa | journal=Physical Review B | publisher=American Physical Society (APS) | volume=65 | issue=18 | date=2002-05-13 | issn=0163-1829 | doi=10.1103/physrevb.65.184109 | page=184109| bibcode=2002PhRvB..65r4109H }}

style="background:lightyellow;|

|I{{overline|4}}3d

|cI16

|Forms at room temperature, 108GPa.{{cite journal | last1=McMahon | first1=M. I. | last2=Gregoryanz | first2=E. | last3=Lundegaard | first3=L. F. | last4=Loa | first4=I. | last5=Guillaume | first5=C. | last6=Nelmes | first6=R. J. | last7=Kleppe | first7=A. K. | last8=Amboage | first8=M. | last9=Wilhelm | first9=H. | last10=Jephcoat | first10=A. P. | title=Structure of sodium above 100 GPa by single-crystal x-ray diffraction | journal=Proceedings of the National Academy of Sciences | volume=104 | issue=44 | date=2007-10-18 | issn=0027-8424 | doi=10.1073/pnas.0709309104 | pages=17297–17299| pmid=17947379 | pmc=2077250 | bibcode=2007PNAS..10417297M |doi-access=free}}

style="background:lightyellow;|

|Pnma

|oP8

|MnP

|Forms at room temperature, 119GPa.{{cite journal | last1=Gregoryanz | first1=E. | last2=Lundegaard | first2=L. F. | last3=McMahon | first3=M. I. | last4=Guillaume | first4=C. | last5=Nelmes | first5=R. J. | last6=Mezouar | first6=M. | title=Structural Diversity of Sodium | journal=Science | publisher=American Association for the Advancement of Science (AAAS) | volume=320 | issue=5879 | date=2008-05-23 | issn=0036-8075 | doi=10.1126/science.1155715 | pages=1054–1057| pmid=18497293 | bibcode=2008Sci...320.1054G | s2cid=29596632 }}

style="background:lightyellow;|

|tI19*

|A host-guest structure that forms above between 125 and 180 GPa.

style="background:lightyellow;|

|hP4

|Forms above 180 GPa.

rowspan="2"|Magnesium

|style="background:lightgreen;|

|style="background:lightgreen;|P6₃/mmc

|style="background:lightgreen;|hP2

|style="background:lightgreen;|Mg

|style="background:lightgreen;|Stable at room temperature and pressure.

style="background:lightyellow;|

|Im{{overline|3}}m

|cI2

|Forms above 50 GPa.{{cite journal | last1=Olijnyk | first1=H. | last2=Holzapfel | first2=W. B. | title=High-pressure structural phase transition in Mg | journal=Physical Review B | publisher=American Physical Society (APS) | volume=31 | issue=7 | date=1985-04-01 | issn=0163-1829 | doi=10.1103/physrevb.31.4682 | pages=4682–4683| pmid=9936412 | bibcode=1985PhRvB..31.4682O }}

rowspan="2"|Aluminium

|style="background:lightgreen;|α-Al

|style="background:lightgreen;|Fm{{overline|3}}m

|style="background:lightgreen;|cF4

|style="background:lightgreen;|Cu

|style="background:lightgreen;|Stable at room temperature and pressure.

style="background:lightyellow;|

|β-Al

|P6₃/mmc

|hP2

|Mg

|Forms above 20.5 GPa.

rowspan="7" |Potassium

|style="background:lightgreen;|

|style="background:lightgreen;|Im{{overline|3}}m

|style="background:lightgreen;|cI2

|style="background:lightgreen;|W

|style="background:lightgreen;|Stable at room temperature and pressure.

style="background:lightyellow;|

|Fm{{overline|3}}m

|cF4

|Cu

|Forms above 11.7 GPa.

style="background:lightyellow;|

|I4/mcm

|tI19*

|A host-guest structure that forms at about 20 GPa.

style="background:lightyellow;|

|P6₃/mmc

|hP4

|NiAs

|Forms above 25 GPa.

style="background:lightyellow;|

|Pnma

|oP8

|MnP

|Forms above 58GPa.

style="background:lightyellow;|

|I4₁/amd

|tI4

|Forms above 112 GPa.

style="background:lightyellow;|

|Cmca

|oC16

|Formas above 112 GPa.

rowspan="4" |Iron

|style="background:lightgreen;|α-Fe, ferrite

|style="background:lightgreen;|Im{{overline|3}}m

|style="background:lightgreen;|cI2

|style="background:lightgreen;|Body-centered cubic

|style="background:lightgreen;|Stable at room temperature and pressure. Ferromagnetic at T<770 °C, paramagnetic from T=770–912 °C.

style="background:pink;|

|γ-iron, austenite

|Fm{{overline|3}}m

|cF4

|Face-centered cubic

|Stable from 912 to 1,394 °C.

style="background:pink;|

| δ-iron

|Im{{overline|3}}m

|cI2

|Body-centered cubic

|Stable from 1,394 – 1,538 °C, same structure as α-Fe.

style="background:lightyellow;|

|ε-iron, Hexaferrum

|P6₃/mmc

|hP2

|Hexagonal close-packed

|Stable at high pressures.

rowspan="3" |Cobalt{{cite journal |last1=de la Peña O’Shea |first1=Víctor Antonio |last2=Moreira |first2=Iberio de P. R. |last3=Roldán |first3=Alberto |last4=Illas |first4=Francesc |title=Electronic and magnetic structure of bulk cobalt: The α, β, and ε-phases from density functional theory calculations |journal=The Journal of Chemical Physics |date=8 July 2010 |volume=133 |issue=2 |page=024701 |doi=10.1063/1.3458691 |pmid=20632764 }}

|style="background:lightgreen;|α-Cobalt

|style="background:lightgreen;|

|style="background:lightgreen;|hexagonal-close packed

|style="background:lightgreen;|Forms below 450 °C.

style="background:pink;|

|β-Cobalt

|face centered cubic

|Forms above 450 °C.

style="background:lightyellow;|

|ε-Cobalt

|P4₁32

|primitive cubic

|Forms from thermal decomposition of [Co₂CO₈]. Nanoallotrope.

rowspan="6"|Rubidium

|style="background:lightgreen;|α-Rb

|style="background:lightgreen;|Im{{overline|3}}m

|style="background:lightgreen;|cI2

|style="background:lightgreen;|W

|style="background:lightgreen;|Stable at room temperature and pressure.

style="background:lightyellow;|

|cF4

|Forms above 7 GPa.

style="background:lightyellow;|

|oC52

|Forms above 13 GPa.

style="background:lightyellow;|

|tI19*

|Forms above 17 GPa.

style="background:lightyellow;|

|tI4

|Forms above 20 GPa.

style="background:lightyellow;|

|oC16

|Forms above 48 GPa.

rowspan="7" |Tin

|style="background:lightblue;|α-tin, gray tin, tin pest

|style="background:lightblue;|Fd{{overline|3}}m

|style="background:lightblue;|cF8

|style="background:lightblue;|d-C

|style="background:lightblue;|Stable below 13.2 °C.

style="background:lightgreen;|

|β-tin, white tin

|I4₁/amd

|tI4

|β-Sn

|Stable at room temperature and pressure.

style="background:lightyellow;|

|γ-tin, rhombic tin

|I4/mmm

|tI2

|In

|Forms above 10 GPa.{{cite journal | last1=Deffrennes | first1=Guillaume | last2=Faure | first2=Philippe | last3=Bottin | first3=François | last4=Joubert | first4=Jean-Marc | last5=Oudot | first5=Benoit | title=Tin (Sn) at high pressure: Review, X-ray diffraction, DFT calculations, and Gibbs energy modeling | journal=Journal of Alloys and Compounds | volume=919 | date=2022 | doi=10.1016/j.jallcom.2022.165675 | page=165675|arxiv=2203.16240}}

style="background:lightyellow;|

|γ'-Sn

|Immm

|oI2

|MoPt₂

|Forms above 30 GPa.

style="background:lightyellow;|

|σ-Sn, γ"-Sn

|Im{{overline|3}}m

|cI2

|Forms above 41 GPa. Forms at very high pressure.{{cite journal|first = A. M.|last = Molodets|author2=Nabatov, S. S.|title = Thermodynamic Potentials, Diagram of State, and Phase Transitions of Tin on Shock Compression|journal = High Temperature|volume = 38|issue = 5|year = 2000|pages = 715–721|doi = 10.1007/BF02755923| bibcode=2000HTemp..38..715M |s2cid = 120417927}}

style="background:lightyellow;|

|δ-Sn

|P6₃/mmc

|hP2

|Mg

|Forms above 157 GPa.

Stanene

rowspan="2" |Polonium

|style="background:lightgreen;|α-Polonium

|style="background:lightgreen;|

|style="background:lightgreen;|simple cubic

|style="background:lightgreen;|

β-Polonium

|rhombohedral

{{colorsample|lightgreen}} Most stable structure under standard conditions.

{{colorsample|lightblue}} Structures stable below room temperature.

{{colorsample|pink}} Structures stable above room temperature.

{{colorsample|lightyellow}} Structures stable above atmospheric pressure.

==Lanthanides and actinides==

File:Actinide phases.svg

Cerium, samarium, dysprosium and ytterbium have three allotropes.
Praseodymium, neodymium, gadolinium and terbium have two allotropes.
Plutonium has six distinct solid allotropes under "normal" pressures. Their densities vary within a ratio of some 4:3, which vastly complicates all kinds of work with the metal (particularly casting, machining, and storage). A seventh plutonium allotrope exists at very high pressures. The transuranium metals Np, Am, and Cm are also allotropic.
Promethium, americium, berkelium and californium have three allotropes each.{{cite journal|doi=10.1088/0305-4608/15/2/002|title=Delocalisation of 5f electrons in curium metal under high pressure|journal=Journal of Physics F: Metal Physics|volume=15|issue=2|pages=L29–L35|year=1985|last1=Benedict|first1=U.|last2=Haire|first2=R. G.|last3=Peterson|first3=J. R.|last4=Itie|first4=J. P.|bibcode=1985JPhF...15L..29B}}

Nanoallotropes

In 2017, the concept of nanoallotropy was proposed.{{Cite journal|last1=Udayabhaskararao|first1=Thumu|last2=Altantzis|first2=Thomas|last3=Houben|first3=Lothar|last4=Coronado-Puchau|first4=Marc|last5=Langer|first5=Judith|last6=Popovitz-Biro|first6=Ronit|last7=Liz-Marzán|first7=Luis M.|last8=Vuković|first8=Lela|last9=Král|first9=Petr|date=2017-10-27|title=Tunable porous nanoallotropes prepared by post-assembly etching of binary nanoparticle superlattices|journal=Science|language=en|volume=358|issue=6362|pages=514–518|doi=10.1126/science.aan6046|issn=0036-8075|pmid=29074773|bibcode=2017Sci...358..514U|doi-access=free|hdl=10067/1472420151162165141|hdl-access=free}} Nanoallotropes, or allotropes of nanomaterials, are nanoporous materials that have the same chemical composition (e.g., Au), but differ in their architecture at the nanoscale (that is, on a scale 10 to 100 times the dimensions of individual atoms).{{Cite web|url=http://israelbds.org/materials-that-dont-exist-in-nature-might-lead-to-new-fabrication-techniques/|title=Materials That Don't Exist in Nature Might Lead to New Fabrication Techniques|website=israelbds.org|language=en-US|access-date=2017-12-08|archive-url=https://web.archive.org/web/20171209152005/http://israelbds.org/materials-that-dont-exist-in-nature-might-lead-to-new-fabrication-techniques/|archive-date=2017-12-09|url-status=dead}} Such nanoallotropes may help create ultra-small electronic devices and find other industrial applications. The different nanoscale architectures translate into different properties, as was demonstrated for surface-enhanced Raman scattering performed on several different nanoallotropes of gold. A two-step method for generating nanoallotropes was also created.

Notes

References

{{Cite EB1911|wstitle=Allotropy}}

External links

{{cite web |author=Nigel Bunce and Jim Hunt |url=http://www.physics.uoguelph.ca/summer/scor/articles/scor40.htm |title=The Science Corner: Allotropes |access-date=January 6, 2017 |url-status=dead |archive-url=https://web.archive.org/web/20080131061355/http://www.physics.uoguelph.ca/summer/scor/articles/scor40.htm |archive-date=January 31, 2008 }}
[http://www.chemistryexplained.com/A-Ar/Allotropes.html Allotropes – Chemistry Encyclopedia]

Category:Chemistry

Category:Inorganic chemistry

Category:Physical chemistry

:Allotropy

History

Differences in properties of an element's allotropes

List of allotropes

=Non-metals=

=Metalloids=

=Metals=

==Lanthanides and actinides==

Nanoallotropes

See also

Notes

References

External links