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

Abstract

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 favorabl...