Disodium helide: Difference between revisions
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{{one source|date=February 2018}} |
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| ImageFile =Disodium helide structure.png |
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| ⚫ | '''Disodium helide'''{{ |
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|Section1={{Chembox Identifiers |
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| SMILES = [Na].[Na].[He] |
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| StdInChI=1S/He.2Na |
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| StdInChIKey=JTZHEFJRNNBIOK-UHFFFAOYSA-N |
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|Section2={{Chembox Properties |
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| Na=2|He=1 |
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| Section3 = {{Chembox Structure |
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| ⚫ | | Structure_ref =<ref name=str>{{cite journal |last1=Wang |first1=Hui-Tian |last2=Boldyrev |first2=Alexander I. |last3=Popov |first3=Ivan A. |last4=Konôpková |first4=Zuzana |last5=Prakapenka |first5=Vitali B. |last6=Zhou |first6=Xiang-Feng |last7=Dronskowski |first7=Richard |last8=Deringer |first8=Volker L. |last9=Gatti |first9=Carlo |last10=Zhu |first10=Qiang |last11=Qian |first11=Guang-Rui |last12=Saleh |first12=Gabriele |last13=Lobanov |first13=Sergey |last14=Stavrou |first14=Elissaios |last15=Goncharov |first15=Alexander F. |last16=Oganov |first16=Artem R. |last17=Dong |first17=Xiao |title=A stable compound of helium and sodium at high pressure – Supplementary Information table 5 |journal=Nature Chemistry |date=May 2017 |volume=9 |issue=5 |pages=440–445 |doi=10.1038/nchem.2716 |pmid=28430195 |bibcode=2017NatCh...9..440D |arxiv=1309.3827 |s2cid=20459726 }}</ref> |
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| CrystalStruct = [[Fluorite]], [[pearson symbol|cF12]] |
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| SpaceGroup = Fm{{overline|3}}m, #225 |
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| PointGroup = |
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| LattConst_a = 3.95 Å at 300 GPa |
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| LattConst_b = |
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| LattConst_c = |
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| LattConst_alpha = |
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| LattConst_beta = |
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| LattConst_gamma = |
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| LattConst_ref = |
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| LattConst_Comment = |
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| UnitCellVolume = |
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| UnitCellFormulas = |
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| Coordination = |
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| MolShape = |
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| OrbitalHybridisation = |
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| Dipole = |
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|Section8={{Chembox Related |
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| OtherCations=[[Lithium helium]] |
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| ⚫ | '''Disodium helide'''<ref>{{cite web |url=https://insidescience.org/news/under-pressure-helium-stops-being-bystander |title=Under Pressure, Helium Stops Being a Bystander |date=2018-03-28 |website=insidescience.org |access-date=2020-11-14 |quote=Then, in 2017, researchers synthesized a stable compound from helium and sodium known as disodium helide under the kinds of high pressures seen within gas giants, suggesting this compound might be found in nature and not just in labs.}}</ref> (Na<sub>2</sub>He) is a compound of [[helium]] and [[sodium]] that is stable at high pressures above {{convert|113|GPa|bar}}. It was first predicted<ref>{{cite journal |last1=Saleh |first1=Gabriele |last2=Dong |first2=Xiao |last3=Oganov |first3=Artem |last4=Gatti |first4=Carlo |last5=Qian |first5=Guang-rui |last6=Zhu |first6=Qiang |last7=Zhou |first7=Xiang-Feng |last8=Wang |first8=Hiu-tian |title=Stable Compound of Helium and Sodium at High Pressure |journal=Acta Crystallographica Section A |date=5 August 2014 |volume=70 |issue=a1 |pages=C617 |doi=10.1107/S2053273314093826|arxiv=1309.3827 }}</ref> using the USPEX [[crystal structure prediction]] algorithm and then synthesised in 2016.<ref name=dong/> |
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== Synthesis == |
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Na<sub>2</sub>He was predicted to be [[thermodynamically stable]] over 160 GPa and dynamically stable over 100 GPa. This means it should be possible to form at the higher pressure and then decompress to 100 GPa, but below that it would decompose. Compared with other [[binary compound]]s of other elements and helium, it was predicted to be stable at the lowest pressure of any such combination. |
Na<sub>2</sub>He was predicted to be [[thermodynamically stable]] over 160 GPa and dynamically stable over 100 GPa. This means it should be possible to form at the higher pressure and then decompress to 100 GPa, but below that it would decompose. Compared with other [[binary compound]]s of other elements and helium, it was predicted to be stable at the lowest pressure of any such combination. This also means, for example, that a helium-potassium compound is predicted to require much higher pressures of the order of terapascals. |
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| ⚫ | The material was synthesized by putting tiny plates of sodium in a [[diamond anvil cell]] along with helium at 1600 bar and then compressing to 130 GPa and heating to 1,500 K with a laser.<ref name="dong" /> Disodium helide is predicted to be an insulator and transparent.<ref name="dong" /> At 200 GPa the sodium atoms have a [[Bader charge analysis|Bader charge]] of +0.599, the helium charge is −0.174, and the two-electron spots are each near −0.511.<ref name="dong" /> This phase could be called disodium helium electride. Disodium helide melts at a high temperature near 1,500 K, much higher than the melting point of sodium. When decompressed, it can keep its form as low as 113 GPa.<ref name="dong" /> As pressure increases, the sodium is predicted to gain more positive charge, the helium to lose negative charge and the free electron density to increase. Energy is compensated by the relative shrinking of the helium atoms and the space for electrons.<ref name=str/> |
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| ⚫ | Disodium helide has a [[Cubic crystal system|cubic crystal structure]], resembling [[fluorite]]. At 300 GPa the edge of a [[unit cell]] of the crystal has {{nowrap|1=''a'' = 3.95 [[Ångström|Å]]}}. Each unit cell contains four helium atoms on the centre of the cube faces and corners, and eight sodium atoms at coordinates halfway between the center and each corner. |
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== Structure == |
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| ⚫ | The material was |
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| ⚫ | Disodium helide has a [[Cubic crystal system|cubic crystal structure]], resembling that of [[fluorite]]. At 300 GPa the edge of a [[unit cell]] of the crystal has {{nowrap|1=''a'' = 3.95 [[Ångström|Å]]}}. Each unit cell contains four helium atoms on the centre of the cube faces and corners, and eight sodium atoms at coordinates halfway between the center and each corner. Electron pairs (2e<sup>−</sup>) are positioned on each edge and the centre of the unit cell.<ref name="note1" group="note" /> Each pair of electrons is [[Spin (physics)|spin]] paired. The presence of these isolated electrons makes this an [[electride]]. The helium atoms do not participate in any bonding; however, the electron pairs can be considered as an eight-centre two-electron [[chemical bond|bond]].<ref name=dong/> |
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==Footnotes== |
==Footnotes== |
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<ref name=note1 group=note>Each face is shared by two cells, each edge is shared by four cells, and each corner is shared by eight cells.</ref> |
<ref name=note1 group=note>Each face is shared by two cells, each edge is shared by four cells, and each corner is shared by eight cells.</ref> |
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<ref name=dong>{{cite journal|last1=Dong|first1=Xiao|last2=Oganov|first2=Artem R.|last3=Goncharov|first3=Alexander F.|last4=Stavrou|first4=Elissaios|last5=Lobanov|first5=Sergey|last6=Saleh|first6=Gabriele|last7=Qian|first7=Guang-Rui|last8=Zhu|first8=Qiang|last9=Gatti|first9=Carlo|last10=Deringer|first10=Volker L.|last11=Dronskowski|first11=Richard|last12=Zhou|first12=Xiang-Feng|last13=Prakapenka|first13=Vitali B.|last14=Konôpková|first14=Zuzana|last15=Popov|first15=Ivan A.|last16=Boldyrev|first16=Alexander I.|last17=Wang|first17=Hui-Tian|title=A stable compound of helium and sodium at high pressure|journal=[[Nature Chemistry]]|volume=9|issue=5|pages=440–445|date=6 February 2017|doi=10.1038/nchem.2716|pmid=28430195|bibcode=2017NatCh...9..440D|arxiv=1309.3827|s2cid=20459726}}</ref> |
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[[Category:Helium compounds]] |
[[Category:Helium compounds]] |
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[[Category:Binary compounds]] |
[[Category:Binary compounds]] |
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[[Category:Substances discovered in 2010s]] |
[[Category:Substances discovered in the 2010s]] |
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[[Category:Electrides]] |
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Latest revision as of 09:18, 15 June 2024
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| Identifiers | |
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3D model (JSmol)
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| Properties | |
| HeNa2 | |
| Molar mass | 49.982141 g·mol−1 |
| Structure[1] | |
| Fluorite, cF12 | |
| Fm3m, #225 | |
a = 3.95 Å at 300 GPa
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| Related compounds | |
Other cations
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Lithium helium |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Disodium helide[2] (Na2He) is a compound of helium and sodium that is stable at high pressures above 113 gigapascals (1,130,000 bar). It was first predicted[3] using the USPEX crystal structure prediction algorithm and then synthesised in 2016.[4]
Synthesis
[edit]Na2He was predicted to be thermodynamically stable over 160 GPa and dynamically stable over 100 GPa. This means it should be possible to form at the higher pressure and then decompress to 100 GPa, but below that it would decompose. Compared with other binary compounds of other elements and helium, it was predicted to be stable at the lowest pressure of any such combination. This also means, for example, that a helium-potassium compound is predicted to require much higher pressures of the order of terapascals.
The material was synthesized by putting tiny plates of sodium in a diamond anvil cell along with helium at 1600 bar and then compressing to 130 GPa and heating to 1,500 K with a laser.[4] Disodium helide is predicted to be an insulator and transparent.[4] At 200 GPa the sodium atoms have a Bader charge of +0.599, the helium charge is −0.174, and the two-electron spots are each near −0.511.[4] This phase could be called disodium helium electride. Disodium helide melts at a high temperature near 1,500 K, much higher than the melting point of sodium. When decompressed, it can keep its form as low as 113 GPa.[4] As pressure increases, the sodium is predicted to gain more positive charge, the helium to lose negative charge and the free electron density to increase. Energy is compensated by the relative shrinking of the helium atoms and the space for electrons.[1]
Structure
[edit]Disodium helide has a cubic crystal structure, resembling that of fluorite. At 300 GPa the edge of a unit cell of the crystal has a = 3.95 Å. Each unit cell contains four helium atoms on the centre of the cube faces and corners, and eight sodium atoms at coordinates halfway between the center and each corner. Electron pairs (2e−) are positioned on each edge and the centre of the unit cell.[note 1] Each pair of electrons is spin paired. The presence of these isolated electrons makes this an electride. The helium atoms do not participate in any bonding; however, the electron pairs can be considered as an eight-centre two-electron bond.[4]
Footnotes
[edit]- ^ Each face is shared by two cells, each edge is shared by four cells, and each corner is shared by eight cells.
References
[edit]- ^ a b Wang, Hui-Tian; Boldyrev, Alexander I.; Popov, Ivan A.; Konôpková, Zuzana; Prakapenka, Vitali B.; Zhou, Xiang-Feng; Dronskowski, Richard; Deringer, Volker L.; Gatti, Carlo; Zhu, Qiang; Qian, Guang-Rui; Saleh, Gabriele; Lobanov, Sergey; Stavrou, Elissaios; Goncharov, Alexander F.; Oganov, Artem R.; Dong, Xiao (May 2017). "A stable compound of helium and sodium at high pressure – Supplementary Information table 5". Nature Chemistry. 9 (5): 440–445. arXiv:1309.3827. Bibcode:2017NatCh...9..440D. doi:10.1038/nchem.2716. PMID 28430195. S2CID 20459726.
- ^ "Under Pressure, Helium Stops Being a Bystander". insidescience.org. 2018-03-28. Retrieved 2020-11-14.
Then, in 2017, researchers synthesized a stable compound from helium and sodium known as disodium helide under the kinds of high pressures seen within gas giants, suggesting this compound might be found in nature and not just in labs.
- ^ Saleh, Gabriele; Dong, Xiao; Oganov, Artem; Gatti, Carlo; Qian, Guang-rui; Zhu, Qiang; Zhou, Xiang-Feng; Wang, Hiu-tian (5 August 2014). "Stable Compound of Helium and Sodium at High Pressure". Acta Crystallographica Section A. 70 (a1): C617. arXiv:1309.3827. doi:10.1107/S2053273314093826.
- ^ a b c d e f Dong, Xiao; Oganov, Artem R.; Goncharov, Alexander F.; Stavrou, Elissaios; Lobanov, Sergey; Saleh, Gabriele; Qian, Guang-Rui; Zhu, Qiang; Gatti, Carlo; Deringer, Volker L.; Dronskowski, Richard; Zhou, Xiang-Feng; Prakapenka, Vitali B.; Konôpková, Zuzana; Popov, Ivan A.; Boldyrev, Alexander I.; Wang, Hui-Tian (6 February 2017). "A stable compound of helium and sodium at high pressure". Nature Chemistry. 9 (5): 440–445. arXiv:1309.3827. Bibcode:2017NatCh...9..440D. doi:10.1038/nchem.2716. PMID 28430195. S2CID 20459726.