Pressure-induced metallization of dense (H 2 S) 2 H 2 with high-T c superconductivity

Abstract

The high pressure structures, metallization, and superconductivity of recently synthesized H 2 -containing compounds (H 2 S) 2 H 2 are elucidated by ab initio calculations. The ordered crystal structure with P1 symmetry is determined, supported by the good agreement between theoretical and experimental X-ray diffraction data, equation of states, and Raman spectra. The Cccm structure is favorable with partial hydrogen bond symmetrization above 37a €...GPa. Upon further compression, H 2 molecules disappear and two intriguing metallic structures with R3m and Im-3m symmetries are reconstructive above 111 and 180a €...GPa, respectively. The predicted metallization pressure is 111a €...GPa, which is approximately one-third of the currently suggested metallization pressure of bulk molecular hydrogen. Application of the Allen-Dynes-modified McMillan equation for the Im-3m structure yields high T c values of 191a €...K to 204a €...K at 200a €...GPa, which is among the highest values reported for H 2 -rich van der Waals compounds and MH 3 type hydride thus far.