Editing Manganese (section)

===Allotropes===
{|align=right
| [[File:Alpha-Mn.png|thumb|x160px|Unit cell of an α-Mn crystal]]
| [[File:Beta-Mn.png|thumb|x160px|Unit cell of a β-Mn crystal]]
|}
Four [[allotropy|allotropes]] (structural forms) of solid manganese are known, labeled α, β, γ and δ, and occur at successively higher temperatures. All are metallic, stable at standard pressure, and have a cubic crystal lattice, but they vary widely in their atomic structures.<ref name="Young 1975">{{cite journal |last1=Young |first1=D.A. |title=Phase diagrams of the elements |url=https://inis.iaea.org/search/search.aspx?orig_q=RN:7255152 |website=International Nuclear Information System |publisher=LNL |access-date=30 January 2023 |page=15 |date=1975}}</ref><ref name="Dhananjayan 1969">{{cite book |last1=Dhananjayan |first1=N. |last2=Banerjee |first2=T. |title=Crystallographic modifications of manganese and their transformation characteristics. ''Chapter 1 of:'' Structure of Electro-Deposited Manganese. |date=1969 |pages=3–28 |publisher=CSIR-NML |url=https://eprints.nmlindia.org/5609/}}</ref><ref name="Kemmitt 1973">{{cite book | last1=Kemmitt | first1=R. D. W. | last2=Peacock | first2=R. D. | title=The Chemistry of Manganese, Technetium and Rhenium. Pergamon Texts in Inorganic Chemistry. | publisher=Elsevier Science | publication-place=Saint Louis | date=1973 | isbn=978-1-4831-3806-0 | oclc=961064866 | page=778}}</ref>

'''Alpha manganese''' (α-Mn) is the equilibrium phase at room temperature. It has a [[body-centered cubic]] lattice and is unusual among elemental metals in that it has a very complex [[unit cell]], with 58 atoms per cell (29 atoms per [[unit cell#Primitive cell|primitive unit cell]]) with manganese atoms in four different types of surroundings (sites).<ref name="Bradley 1927">{{cite journal | first1=A.J. | last1=Bradley | first2=J. | last2=Thewlis | title=The crystal structure of α-manganese | journal=Proceedings of the Royal Society of London, Series A | volume=115 | issue=771 | year=1927 | issn=0950-1207 | doi=10.1098/rspa.1927.0103 | pages=456–471| bibcode=1927RSPSA.115..456B | doi-access=free }}</ref><ref name="Young 1975" /> It is [[paramagnetic]] at room temperature and [[antiferromagnetic]] at temperatures below {{convert|95|K|C|sigfig=3}}.<ref name="Lawson 1994">{{cite journal | last1=Lawson | first1=A. C. | last2=Larson | first2=Allen C. | last3=Aronson | first3=M. C. | display-authors=etal | title=Magnetic and crystallographic order in α-manganese | journal=J. Appl. Phys. | volume=76 | issue=10 | date=1994 | pages=7049–7051 | issn=0021-8979 | doi=10.1063/1.358024| bibcode=1994JAP....76.7049L }}</ref>
[[File:Phase diagram of manganese (1975).png|thumb|left|upright|Phase diagram of manganese<ref name="Young 1975" />]]

'''Beta manganese''' (β-Mn) forms when heated above the transition temperature of {{convert|973|K|C F|sigfig=3}}<!-- For the α-β transition, "Young 1975" gives about 1000 K; "Kemmitt 1973" gives 700±3 C (973 K)-->.  It has a primitive cubic structure with 20 atoms per unit cell at two types of sites, which is as complex as that of any other elemental metal.<ref name="Prior 2004">{{cite journal | last1=Prior | first1=Timothy J | last2=Nguyen-Manh | first2=Duc | last3=Couper | first3=Victoria J | last4=Battle | first4=Peter D | title=Ferromagnetism in the beta-manganese structure: Fe<sub>1.5</sub>Pd<sub>0.5</sub>Mo<sub>3</sub>N | journal=Journal of Physics: Condensed Matter | volume=16 | issue=13 | date=2004 | issn=0953-8984 | doi=10.1088/0953-8984/16/13/008 | pages=2273–2281| bibcode=2004JPCM...16.2273P | s2cid=250784683 }}</ref> It is easily obtained as a metastable phase at room temperature by rapid quenching of manganese at {{convert|850|C|K F|sigfig=3}} in ice water. It does not show [[Magnetism|magnetic ordering]], remaining paramagnetic down to the lowest temperature measured (1.1&nbsp;K).<ref name="Prior 2004" /><ref name="Funahashi 1984">{{cite journal | last1=Funahashi | first1=S. | last2=Kohara | first2=T. | title=Neutron diffuse scattering in β-manganese | journal=J. Appl. Phys. | volume=55 | issue=6 | date=1984 | issn=0021-8979 | doi=10.1063/1.333561 | pages=2048–2050| bibcode=1984JAP....55.2048F }}</ref><ref name="Duschanek 1989">{{cite journal | last1=Duschanek | first1=H. | last2=Mohn | first2=P. | last3=Schwarz | first3=K. | title=Antiferromagnetic and ferromagnetic gamma-manganese generalisation of the fixed-spin-moment method | journal=Physica B: Condensed Matter | volume=161 | issue=1–3 | year=1989 | issn=0921-4526 | doi=10.1016/0921-4526(89)90120-8 | pages=139–142}}</ref>

'''Gamma manganese''' (γ-Mn) forms when heated above {{convert|1370|K|C F|sigfig=3}}.<!-- For the beta-gamma transition, "Duschanek 1989" gives 1368 K; "Garlen 2015" gives 1373 K; both round to 1370 K --> It has a simple face-centered cubic structure (four atoms per unit cell). When quenched to room temperature it converts to β-Mn, but it can be stabilized at room temperature by alloying it with at least 5 percent of other elements (such as C, Fe, Ni, Cu, Pd or Au). These solute-stabilized alloys distort into a face-centered [[Tetragonal crystal system|tetragonal]] structure.<ref name="Bacon 1970">{{cite journal | last1=Bacon | first1=G E | last2=Cowlam | first2=N | title=A study of some alloys of gamma -manganese by neutron diffraction | journal=Journal of Physics C: Solid State Physics | volume=3 | issue=3 | date=1970| issn=0022-3719 | doi=10.1088/0022-3719/3/3/023 | pages=675–686| bibcode=1970JPhC....3..675B }}</ref><ref name="Duschanek 1989"/>

'''Delta manganese''' (δ-Mn) forms when heated above {{convert|1406|K|C F|sigfig=3}}<!-- For the γ-δ transition, "Dhananjayan 1969" says 1134 C (= approx 1407 K); "Duschanek 1989" indicates 1406 K; "Young 1975" shows about 1400±20 K in the phase diagram (though its text states "near 1520 K", which seems to be a typo because it matches the melting point, not the gamma-delta transition). --> and is stable up to the manganese melting point of {{convert|1519|K|C F|sigfig=3}}. It has a [[body-centered cubic]] structure (two atoms per cubic unit cell).<ref name="Dhananjayan 1969" /><ref name="Duschanek 1989" />