Structure re-determination and superconductivity observation of bulk 1T MoS₂

2H MoS₂ has been intensively studied because of its layer-dependent electronic structures and novel physical properties. Though the metastable 1T MoS₂ with a [MoS₆] octahedron was observed over the microscopic area, the true crystal structure of 1T phase has not been strictly determined. Moreover, the true physical properties have not been demonstrated from experiments owing to the challenge for the preparation of pure 1T MoS₂ crystals. 1T MoS₂ single crystals were successfully synthesized and the crystal structure of 1T MoS₂ re-determined from single-crystal X-ray diffraction. 1T MoS₂ crystallizes in the space group P anti 3m1 with a cell of a=b=3.190(3) Aa and c=5.945(6) Aa. The individual MoS₂ layer consists of MoS₆ octahedra sharing edges with each other. More surprisingly, the bulk 1T MoS₂ crystals undergo a superconducting transition of T_c=4 K, which is the first observation of superconductivity in pure 1T MoS₂ phase. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)