Direct synthesis of pure H3S from S and H elements: No evidence of the cubic superconducting phase up to 160 GPa

The H3S compound was reproducibly synthesized by laser heating hydrogen-embedded solid sulfur samples at various pressures above 75 GPa in a diamond anvil cell. X-ray diffraction studies were conducted up to 160 GPa and the crystal structure has been identified with space group Cccm. The stability of this sole orthorhombic H3S phase up to 160 GPa contradicts ab initio calculations that predict the stability of a sequence of two metallic superconductive structures above 110 GPa, with R3m and Im (3) over barm symmetries. This work also has strong implications for the current understanding of the 200 K superconductivity phenomenon in H2S since it seems to rule out the hypothesis of the decomposition of H2S into sulfur and superconducting H3S.