Pressure-induced superconducting ternary hydride H3SXe: A theoretical investigation

Abstract

In general, heavy elements contribute only to acoustic phonon modes, which are less important for the superconductivity of hydrides. However, it was revealed that the heavier elements could enhance the phonon-mediated superconductivity in ternary hydrides. In the H3S–Xe system, a novel H3SXe compound was discovered by first-principle calculations. The structural phase transitions of H3SXe under high pressures were studied. The R-3m phase of H3SXe was predicted to appear at pressures above 80 GPa, which transitions to C2/m, P-3m1, and Pm-3m phases at pressures of 90, 160, and 220 GPa, respectively. It has been anticipated that the Pm-3m-H3SXe phase with a similar structural feature as that of Im-3m-H3S is a potential high-temperature superconductor with a Tc of 89 K at 240 GPa. The Tc value of H3SXe is lower than that of H3S at high pressure. The “H3S” host lattice of Pm-3m-H3SXe is a crucial factor influencing the Tc value. The Xe atoms could accelerate the hydrogen-bond symmetrization. With the increase of the atomic number, the Tc value linearly increases in the H3S–noble-gas-element system. This indicates that the superconductivity can be modulated by changing the relative atomic mass of the noble-gas element.