Superconducting high-pressure phases of disilane

Abstract

High-pressure structures of disilane (Si(2)H(6)) are investigated extensively by means of first-principles density functional theory and a random structure-searching method. Three metallic structures with P-1, Pm-3m, and C2/c symmetries are found, which are more stable than those of XY(3)-type candidates under high pressure. Enthalpy calculations suggest a remarkably wide decomposition (Si and H(2)) pressure range below 135 GPa, above which three metallic structures are stable. Perturbative linear-response calculations for Pm-3m disilane at 275 GPa show a large electron-phonon coupling parameter lambda of 1.397 and the resulting superconducting critical temperature beyond the order of 10(2) K.

Fig. 1.

Main figure: Calculated enthalpies per Si₂H₆ unit of various disilane structures as functions of pressure with respect to the decomposition (2Si + 3H₂) enthalpies (red dotted line), which are calculated by adopting the Si and H₂ structures from refs.  and , respectively. Inset: Enthalpies in the pressure range from 250 GPa to 400 GPa.

Fig. 2.

The structures of disilane under high pressures. (A) The P-1 phase at 175 GPa, (B) Pm-3m phase at 275 GPa, and (C) C2/c phase at 300 GPa. Large and small atoms are Si and H, respectively.

Fig. 3.

The phonon band structure and projected phonon DOS charts of (A) P-1 phase at 175 GPa, (B) Pm-3m phase at 275 GPa, and (C) C2/c phase at 300 GPa, respectively.

Fig. 4.

The Eliashberg phonon spectral function α²F(ω) and the electron-phonon integral λ(ω) for phases of P-1, Pm-3m and C2/c calculated at 175, 275, and 300 GPa, respectively.