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Title: A stable compound of helium and sodium at high pressure

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 2He, 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 2HeO with a similar structure at pressures above 15 GPa.

Authors:
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Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
National Science Foundation (NSF); Defense Advanced Research Projects Agency (DARPA)
OSTI Identifier:
1355028
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nature Chemistry; Journal Volume: 9; Journal Issue: 5
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; chemical physics; electron transfer; solid-state chemistry

Citation Formats

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., and Wang, Hui-Tian. A stable compound of helium and sodium at high pressure. United States: N. p., 2017. Web. doi:10.1038/nchem.2716.
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. A stable compound of helium and sodium at high pressure. United States. doi:10.1038/nchem.2716.
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., and Wang, Hui-Tian. Mon . "A stable compound of helium and sodium at high pressure". United States. doi:10.1038/nchem.2716.
@article{osti_1355028,
title = {A stable compound of helium and sodium at high pressure},
author = {Dong, Xiao and Oganov, Artem R. and Goncharov, Alexander F. and Stavrou, Elissaios and Lobanov, Sergey and Saleh, Gabriele and Qian, Guang-Rui and Zhu, Qiang and Gatti, Carlo and Deringer, Volker L. and Dronskowski, Richard and Zhou, Xiang-Feng and Prakapenka, Vitali B. and Konôpková, Zuzana and Popov, Ivan A. and Boldyrev, Alexander I. and Wang, Hui-Tian},
abstractNote = {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, Na2He, 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 Na8 cubes. We also predict the existence of Na2HeO with a similar structure at pressures above 15 GPa.},
doi = {10.1038/nchem.2716},
journal = {Nature Chemistry},
number = 5,
volume = 9,
place = {United States},
year = {Mon Feb 06 00:00:00 EST 2017},
month = {Mon Feb 06 00:00:00 EST 2017}
}