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

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 37 GPa. Upon further compression, H(2) molecules disappear and two intriguing metallic structures with R3m and Im-3m symmetries are reconstructive above 111 and 180 GPa, respectively. The predicted metallization pressure is 111 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 191 K to 204 K at 200 GPa, which is among the highest values reported for H(2)-rich van der Waals compounds and MH(3) type hydride thus far.