Synthesis, Electronic and Crystal Structures, and Physical Studies of the Superconductor Cs1Mo12S14, Final Step of the Condensation of the Mo6L8iL6a Unit
Résumé
The ternary reduced molybdenum sulphide Cs1Mo12S14 has been synthesized by solid-state reaction at 1400 °C for 96 h in sealed molybdenum crucibles. The compound crystallizes in the trigonal space group P3̅1c with the following lattice parameters: a = 9.9793 (2) Å, c = 6.3730 (2) Å, Z = 1. Its crystal structure was determined from single crystal X-ray diffraction data and consists of interconnected Mo6S8iS6a units forming an original three-dimensional framework in which large tunnels are occupied randomly by the Cs+ ions. 133Cs static NMR studies are in favor of a static cesium disorder. Unlike Ba4Mo12S18 where some Mo6S8iS6a units are also connected through Si-i ligands, this connection mode does not lead to significant interactions in the title compound. Single-crystal resistivity measurements show that Cs1Mo12S14 presents a metallic behavior with a superconducting transition at 7.7 K as confirmed by magnetic measurements.