We use the diffusion quantum Monte Carlo to revisit the enthalpy-pressure phase diagram of the various products from the different proposed decompositions of H2S at pressures above 150~GPa. Our results entails a revision of the ground-state enthalpy-pressure phase diagram. Specifically, we find that the C2/c HS2 structure is persistent up to 440~GPa before undergoing a phase transition into the C2/m phase. Contrary to density functional theory, our calculations suggest that the C2/m phase of HS is more stable than the I41/amd HS structure over the whole pressure range from 150 to 400 GPa. Moreover, we predict that the Im-3m phase is the most likely candidate for H3S, which is consistent with recent experimental x-ray diffraction measurements.
@article{arxiv.1610.01967,
title = {High-Pressure Hydrogen Sulfide by Diffusion Quantum Monte Carlo},
author = {Sam Azadi and Thomas D. Kühne},
journal= {arXiv preprint arXiv:1610.01967},
year = {2017}
}