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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. As a result, we also predict the existence of Na 2HeO with a similar structure at pressures above 15 GPa.

Authors:
 [1]; ORCiD logo [2];  [3];  [4];  [5];  [6];  [7];  [7];  [8];  [9];  [9]; ORCiD logo [10];  [11];  [12]; ORCiD logo [13];  [14];  [15]
  1. Nankai Univ., Tianjin (China); Center for High Pressure Science and Technology Advanced Research, Beijing (China); Stony Brook Univ., Stony Brook, NY (United States)
  2. Stony Brook Univ., Stony Brook, NY (United States); Skolkovo Institute of Science and Technology, Moscow (Russia); Moscow Institute of Physics and Technology, Moscow Region (Russia); Northwestern Polytechnical Univ., Xi'an (China); Carnegie Institute of Washington, Washington, D.C. (United States)
  3. Chinese Academy of Sciences, Anhui (China)
  4. Carnegie Institute of Washington, Washington, D.C. (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  5. Carnegie Institute of Washington, Washington, D.C. (United States); Siberian Branch Russian Academy of Science, Novosibirsk (Russia)
  6. Moscow Institute of Physics and Technology, Moscow Region (Russia)
  7. Stony Brook Univ., Stony Brook, NY (United States)
  8. Univ. di Milano, Milan (Italy)
  9. RWTH Aachen Univ., Aachen (Germany)
  10. Nankai Univ., Tianjin (China); Stony Brook Univ., Stony Brook, NY (United States)
  11. Univ. of Chicago, Chicago, IL (United States)
  12. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
  13. Utah State Univ., Logan, UT (United States); RUDN Univ., Moscow (Russia)
  14. Utah State Univ., Logan, UT (United States)
  15. Nankai Univ., Tianjin (China); Nanjing Univ., Nanjing (China)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1357332
Report Number(s):
LLNL-JRNL-680457
Journal ID: ISSN 1755-4330
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature Chemistry
Additional Journal Information:
Journal Volume: 9; Journal Issue: 5; Journal ID: ISSN 1755-4330
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 58 GEOSCIENCES; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 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. https://www.osti.gov/servlets/purl/1357332.
@article{osti_1357332,
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. As a result, 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}
}

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