Anionic chemistry of noble gases: formation of Mg-NG (NG = Xe, Kr, Ar) compounds under pressure.
While often considered to be chemically inert, the reactivity of noble gas elements at elevated pressures is an important aspect of fundamental chemistry. The discovery of Xe oxidation transformed the doctrinal boundary of chemistry by showing that a complete electron shell is not inert to reaction. However, the reductive propensity, i.e., gaining electrons and forming anions, has not been proposed or examined for noble gas elements. In this work, we demonstrate, using first-principles electronic structure calculations coupled to an efficient structure prediction method, that Xe, Kr, and Ar can form thermodynamically stable compounds with Mg at high pressure (≥125, ≥250, and ≥250 GPa, respectively). The resulting compounds are metallic and the noble gas atoms are negatively charged, suggesting that chemical species with a completely filled shell can gain electrons, filling their outermost shell(s). Moreover, this work indicates that Mg2NG (NG = Xe, Kr, Ar) are high-pressure electrides with some of the electrons localized at interstitial sites enclosed by the surrounding atoms. Previous predictions showed that such electrides only form in Mg and its compounds at very high pressures (>500 GPa). These calculations also demonstrate strong chemical interactions between the Xe 5d orbitals and the quantized interstitial quasiatom (ISQ) orbitals, including the strong chemical bonding and electron transfer, revealing the chemical nature of the ISQ.
Department of Chemistry and Biochemistry, California State University , Northridge, California 91330, United States.|Beijing Computational Science Research Center , Beijing 10094, P. R. China.
Mao-Sheng
MS
Miao
Institute of Condensed Matter Physics, Linyi University , Linyi 276005, P. R. China.|Department of Earth Science, University of California , Santa Barbara, California 93106, United States.
Xiao-Li
XL
Wang
Department of Chemistry, University of Houston , Houston, Texas 77204-5003, United States.
Jakoah
J
Brgoch
Department of Earth Science, University of California , Santa Barbara, California 93106, United States.
Frank
F
Spera
Department of Earth Science, University of California , Santa Barbara, California 93106, United States.
Matthew G
MG
Jackson
Faculty of Physics, University of Vienna , Sensengasse 8/12 A-1090 Wien, Austria.
Georg
G
Kresse
Beijing Computational Science Research Center , Beijing 10094, P. R. China.
Hai-Qing
HQ
Lin