Solid hydrogen sulfide is a typical molecular crystal, but its stability under pressure remains controversial. In particular, the recent experimental discovery of high-pressure superconductivity at 190 K in an ${\mathrm{H}}_2\mathrm{S}$ sample (arXiv:1412.0460) inspired efforts to revalidate this controversial issue, the pressure at which ${\mathrm{H}}_2\mathrm{S}$ decomposes and the resultant decomposition products urgent need to be evaluated. In this paper we performed an extensive structural study on different stoichiometries of H_nS with $n>1$ under high pressure using ab initio calculations. Our results show that ${\mathrm{H}}_2\mathrm{S}$ is stable below 43 GPa and at elevated pressure it decomposes into ${\mathrm{H}}_3\mathrm{S}$ and sulfur. ${\mathrm{H}}_3\mathrm{S}$ is stable at least up to 300 GPa, while other H-rich compounds, including ${\mathrm{H}}_4\mathrm{S}, {\mathrm{H}}_5\mathrm{S}$, and ${\mathrm{H}}_6\mathrm{S}$, are unstable in the pressure range of this study.

• Received 13 January 2015
• Revised 30 March 2015

DOI:https://doi.org/10.1103/PhysRevB.91.180502