Pressure-induced phase transition in solid hydrogen sulfide at 11 GPa

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Abstract
The Raman spectra of hydrogen‐bonded molecular solid H2S have been measured up to 23 GPa at 300 K in a gasketed diamond‐anvil cell. In the orientationally disordered phase I between 0.47 and 11 GPa, the symmetric stretching mode ν1 shows a red‐shift in frequency (dν1/dP=−10.1 cm−1/GPa ) and a dramatic broadening with pressure. At about 11 GPa, the antisymmetric stretching band ν3 appears at the higher‐frequency side of ν1. Near this same pressure five low‐frequency vibrational modes also appear and show pressure‐sensitive features. These results indicate a pressure‐induced phase transition near 11 GPa. This new solid phase, which persists to at least 23 GPa at 300 K, seems to be the same phase as previously found above 3.3 GPa at 25 K.