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

TLDR

The study uses ab initio calculations to elucidate the high‑pressure structures, metallization, and superconductivity of the newly synthesized H₂‑containing compound (H₂S)₂H₂. The authors performed density‑functional theory calculations to model the pressure‑dependent crystal structures, electronic states, and vibrational spectra of (H₂S)₂H₂. The calculations reveal that (H₂S)₂H₂ adopts a P1 structure at low pressure, transforms to a Cccm phase above 37 GPa, and becomes metallic with R3m and Im‑3m symmetries above 111 GPa and 180 GPa, respectively, achieving a metallization pressure of 111 GPa and predicting superconducting transition temperatures of 191–204 K at 200 GPa.

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 GPa. Upon further compression, H2 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 Tc values of 191 K to 204 K at 200 GPa, which is among the highest values reported for H2-rich van der Waals compounds and MH3 type hydride thus far.