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

Abstract

The metal-based noble gas compounds exhibit interesting behavior of electronic valence states under pressure. For example, Xe upon compression can gain electrons from the alkali metal, or lose electrons unexpectedly to Fe and Ni, toward formation of stable metal compounds. In addition, the Na 2 He is not even stabilized by the local chemical bonds but via the long-range Coulomb interactions. Herein, by using the first-principles calculations and the unbiased structure searching techniques, we uncover that the transition metal Y is able to react with Xe above 60 GPa within various Y-Xe stochiometries, namely the YXe, YXe 2 , YXe 3 and Y 3 Xe structures. Surprisingly, it is found that all the resulting compounds are intermetallic and Xe atoms are positively charged. We also argue that the pressure-induced changes of the energy orbital filling are responsible for the electron transfer from Xe to Y.Meanwhile, the Peierls-like mechanism is found to stabilize the energetically most favorable YXe-Pbam phase. Furthermore, the predicted YXe-Pbam, YXe-Pnnm, and YXe 3 -I4/mcm phases are discovered to be a phonon-mediated superconductors under pressure, with the critical superconducting temperatures in the range of approximately ** Corresponding author email: puchunying@126.com 3-4K, 7-10K, and 5-6K, respectively. In summary, our work promotes further understanding of the crystal structures and electronic properties of the metal-based noble gas compounds. compounds were synthesized by oxidizing the nobel gas elements with the highly electronegative elements such as fluorine 7-8 and oxygen 9-12 . Yet later, it was also found that the high-pressure compression constitutes another suitable and promising route for the synthesis of NG compounds. For example, the compression of noble gases and some molecular species leads to the formation of multiple van der Waals solids at relatively low pressure, such as: HeN 4 13 , He-H 2 O 14 , Ar(H 2 ) 2 15 , ArO 2 , Ar(O 2 ) 16 , Kr(H 2 ) 4 17 , Xe(H 2 ) 8 18 , Xe-N 2 19 , Xe-CH 4 20 , Xe-H 2 O 21 and Xe(O 2 ) 2 16 .

A newly predicted stable calcium argon compound by ab initio calculations under high pressure

“…For CaAr 3 , two metastable structures were identified in the selected pressure range, existing as the Pm1 phase in the 110-170 GPa range and changing from the Pm1 phase to the P4/mmm phase at 170 GPa. The phase transition is same as that of YXe 3 [16]. At 110GPa, the lattice parameters of Pm1- In common with the CsXe 4 structure [18], the CaAr 4 is a monoclinic P2 1 /m phase at 180-200 GPa as shown in figure 3(f) and the lattice parameters of P2 1 /m-CaAr 4 are a = 4.581 Å, b = 3.834 Å, and c = 5.864 Å, the specific lattice parameters are shown in table 1.…”

“…In these compounds, NG elements have very rich chemical properties and can act as a reducing agent or assume the role of an oxidizing agent. Under the action of pressure, the valence orbital energy of NG element increases rapidly and becomes significantly higher than that of oxidant element, such as Xe-O [10,11], Kr-O [12], Xe-N [13], Xe-C [14], Xe-Ni/Fe [15], Xe-Y [16] systems, NG atoms act as reducing agents, donating electrons, and are positively charged. In contrast, in the compounds formed by Xe atoms with Li [17], Cs [18], Mg [19] atoms, and Ar with Ni [20], the NG elements gain electrons from the metal elements with lower ionization energies, acting as oxidizing agents and exhibiting anionic properties.…”

Materials under high pressure: A chemical perspective

“…No other noble gas elements were reactive with iron peroxide, suggesting that it might specifically be "blamed" for the missing xenon. Several other elements have been predicted to form compounds with xenon under pressure, including magnesium, [250] nitrogen, [251] cesium [252], and yttrium, [253] while compound formation has been experimentally observed when xenon is combined with water [254] and hydrogen [255].…”

Coexistence of superconductivity and electride states in Ca2H with an antifluorite-type motif under compression

“…31–33 Based on this, a great deal of novel electride superconductors (ESCs) have been subsequently discovered, where superconducting Y-, Li-, and Ca-based electrides are the primary components. For example, 0D electrides Pnnm Y 3 Xe 34 and P 6 3 / mmc Y 3 Si 35 were reported to have computed T c values of 10.8 K at 75 GPa and 14.5 K at 50 GPa, respectively. For Li-containing electrides, 36–39 C 2/ c Li 6 P with dumbbell-like interstitial electrons that play a crucial role in promoting superconductivity has a notable predicted T c of 39.3 K at 270 GPa.…”