A stable compound of helium and sodium at high pressure

Helium is generally understood to be chemically inert and this is due to its extremely stable closed-shell electronic configuration, zero electron affinity and an unsurpassed ionization potential. It is not known to form thermodynamically stable compounds, except a few inclusion compounds. Here, usi...

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Published in:Nature chemistry Vol. 9; no. 5; pp. 440 - 445
Main Authors: 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
Format: Journal Article
Language:English
Published: London Nature Publishing Group UK 01.05.2017
Nature Publishing Group
Subjects:
119/118
140/133
639/638/263/915
639/638/440/94
639/638/440/947
Analytical Chemistry
Biochemistry
chemical physics
Chemistry
Chemistry/Food Science
electron transfer
Electrons
Helium
High pressure
Inorganic Chemistry
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Ionization
Laboratories
Organic Chemistry
Physical Chemistry
Physics
Science
Sodium
solid-state chemistry
United States > US
China
Germany
Utah
Russia
ISSN:1755-4330, 1755-4349, 1755-4349
Online Access:Get full text
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Summary:Helium is generally understood to be chemically inert and this is due to its extremely stable closed-shell electronic configuration, zero electron affinity and an unsurpassed ionization potential. It is not known to form thermodynamically stable compounds, except a few inclusion compounds. Here, using the ab initio evolutionary algorithm USPEX and subsequent high-pressure synthesis in a diamond anvil cell, we report the discovery of a thermodynamically stable compound of helium and sodium, Na 2 He, which has a fluorite-type structure and is stable at pressures >113 GPa. We show that the presence of He atoms causes strong electron localization and makes this material insulating. This phase is an electride, with electron pairs localized in interstices, forming eight-centre two-electron bonds within empty Na 8 cubes. We also predict the existence of Na 2 HeO with a similar structure at pressures above 15 GPa. Helium is generally recognized as being chemically inert. A thermodynamically stable compound of helium and sodium, Na 2 He, has been predicted computationally and then synthesized at high pressure. It exists as an electride, where strongly localized electrons serve as anions located at the centre of Na 8 cubes.
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National Science Foundation (NSF)
Defense Advanced Research Projects Agency (DARPA)
ISSN:1755-4330
1755-4349
1755-4349
DOI:10.1038/nchem.2716