Pressure-induced metallization of dense (H2S)2H2 with high-Tc superconductivity

Abstract

The high pressure structures, metallization, and superconductivity of recently synthesized H2-containing compounds (H2S)2H2 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 37[emsp14]GPa. Upon further compression, H2 molecules disappear and two intriguing metallic structures with R3m and Im-3m symmetries are reconstructive above 111 and 180[emsp14]GPa, respectively. The predicted metallization pressure is 111[emsp14]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 Tc values of 191[emsp14]K to 204[emsp14]K at 200[emsp14]GPa, which is among the highest values reported for H2-rich van der Waals compounds and MH3 type hydride thus far.