Pressure-induced superconducting ternary hydride H3SXe: A theoretical investigation

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 T_c of 89 K at 240 GPa. The T_c 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 T_c value. The Xe atoms could accelerate the hydrogen-bond symmetrization. With the increase of the atomic number, the T_c 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.