writer：Shi-Ping Wang, Xu-Yan Xue, Cai-Zhuang Wang, and Wen-Cai Lu
keywords：High temperature superconductivity
source：期刊
specific source：Japanese Journal of Applied Physics,(2018) 57 083101.
Issue time：2018年

High temperature superconductivity of H2S at high pressure is fascinating, and there is still controversy about crystalline structures and stoichiometry responsible for high Tc. Determining the crystal structures of H2S at high pressure is a tremendous challenge in experiments. We

found a previously missing structure with C2/m space group symmetry by genetic algorithm and first-principles calculations, which is an intermediate structure between the P1 and Cmca structures and is competitive with the P1 and Cmca phases at 150–175 GPa. The main difference between the C2/m and P1 structure is the S–H3 bond lengths in the two structures. The C2/m and Cmca structures consist of similar structural units (H4S6 rectangular units). In the C2/m structure the chains formed by the H4S6 rectangular units are parallel, while in the Cmca structure the H4S6 rectangular units are twisted. The possible structural transformations from P1 to C2/m to Cmca structure were also discussed. By calculating the electronic structure, phonon spectrum and electron–phonon coupling parameters, the C2/m structure was predicted to have a superconducting transition temperature Tc of 53–74K at 150 GPa.