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Unexpected Xe Cations and Superconductivity in Y–Xe Intermediate Compounds under Pressure

Zhou, Dawei, Szczęśniak, Dominik, Yu, Jiahui, Pu, Chunying, Tang, Xin
Journal of physical chemistry 2019 v.123 no.14 pp. 9323-9330
cations, energy, oxidants, physical chemistry, superconductivity, temperature
Pressure can dramatically affect the energy orbital filling in condensed matter systems, leading to the formation of novel compounds with unexpected behavior of electronic valence states. Herein, by using the unbiased structure searching techniques, we predict that the stable YXe, YXe₂, YXe₃, and Y₃Xe intermetallic compounds can be formed under pressure. In the predicted Y–Xe systems, the Xe atoms are surprisingly observed to be positively charged, whereas the Y atoms act as oxidants. It is argued that such electron transfers from the Xe to Y atoms are caused by the pressure-induced changes of the energy orbital filling. Meanwhile, all predicted Y–Xe systems exhibit metallic character, where the YXe-Pbam, YXe-Pnnm, and YXe₃-I4/mcm phases are additionally suggested to be potential phonon-mediated superconductors at high pressure, characterized by the critical transition temperatures of few Kelvins. Interestingly, it is also observed that the Peierls-type mechanism stabilizes the energetically most favorable YXe-Pbam phase. Thus, the present study promotes further understanding of the valence state behavior and the resulting electronic phenomena in the condensed matter systems at high pressure, with a special attention given to noble gas compounds.