Pressure-induced decomposition of solid hydrogen sulfide

TL;DR

This study uses ab initio calculations to determine the stability and decomposition pressures of solid hydrogen sulfide and related compounds, revealing that H2S decomposes into H3S and sulfur above 50 GPa, with H3S stable up to 300 GPa.

Contribution

The paper provides the first comprehensive high-pressure structural analysis of various HnS compounds, clarifying their stability ranges and decomposition pathways.

Findings

H2S is stable below 50 GPa and decomposes at higher pressures.

H3S remains stable up to at least 300 GPa.

Other hydrogen-rich sulfides are unstable between 20 and 300 GPa.

Abstract

Solid hydrogen sulfide is well known as a typical molecular crystal but its stability under pressure is still under debate. Particularly, Eremets et al. found the high pressure superconductivity with $T_{c}\approx$ 190 K in a H$_{2}$S sample [arXiv: 1412.0460 (2014)] which is associates with the elemental decomposition into H$_{3}$S [Sci. Rep. 4, 6968 (2014)]. Therefore, on what pressure H$_{2}$S can decompose and which kind of the products of decomposition urgent need to be solved. In this paper, we have performed an extensive structural study on different stoichiometries H$_{n}$S with ${n> 1}$ under high pressure using $ab$ $initio$ calculations. Our results show that H$_{2}$S is stable below 50 GPa and decomposes into H$_3$S and sulfur at high pressure, while H$_{3}$S is stable at least up to 300 GPa. The other hydrogen-rich H$_{4}$S, H$_{5}$S, and H$_{6}$S are unstable in the pressure range from 20 to 300 GPa.