A stable compound of helium and sodium at high pressure

Xiao Dong, Artem R. Oganov*, Alexander F. Goncharov, Elissaios Stavrou, Sergey Lobanov, Gabriele Saleh, Guang Rui Qian, Qiang Zhu, Carlo Gatti, Volker L. Deringer, Richard Dronskowski, Xiang Feng Zhou, Vitali B. Prakapenka, Zuzana Konôpková, Ivan A. Popov, Alexander I. Boldyrev, Hui Tian Wang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

155 Scopus citations

Abstract

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 >113â €..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 15â €..GPa.

Original languageEnglish
Pages (from-to)440-445
Number of pages6
JournalNature Chemistry
Volume9
Issue number5
DOIs
StatePublished - 1 May 2017
Externally publishedYes

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