Favored decomposition paths of hydrogen sulfide at high pressure

Abstract

Sulfur trihydride (H3S) is a theoretically predicted high-pressure superconductor and has been experimentally confirmed to have the highest superconducting transition temperature Tc. Solid H2S decomposition is considered as the primary source of H3S, however, it is complex and controversial how H2S is transformed into H3S. Herein, we employ the density functional theory augmented with many-body dispersion interactions (DFT+MBD) to study a full path of H2S decomposition at pressure of 20–260 GPa. We find that H2S starts to decompose into H3S and other H–S compounds from about 20 GPa, in which the MBD interactions can decrease both the phase transition pressure of H–S compounds and the reaction transition pressure of H2S decomposition. H3S2, H4S3, H3S5, sulfur and HS2 are byproducts of H2S decomposition with increasing pressure. Our results provide a complete phase diagram of H–S compounds during H2S decomposition, and clarify the pressure range of each product and favored paths of H2S decomposition.