Crystal Data for Mixed-Anion Molybdenum Dichalcogenides

The layered dichalcogenides¹ MoS₂ and MoSe₂ are of special interest as lubricants, ² catalysts, and catalyst supports for hydrodesulfurization reactions, ³ precursors of intercalation superconductors, ⁴ and possible electrodes for photoelectrolysis.⁵ In the pure, stoichiometric state they are moderate-gap semiconductors (1.75 eV for MoS₂ and 1.4 eV for MoSe₂), ⁵ presumably because the characteristic trigonal splitting of the d orbitals leads to filled d subbands. As part of a larger study on how small changes in chemical parameters affect superconductivity, we have had occasion to prepare the full solid solution series MoS_2-xSe_x (0 < × < 2). The end compounds form both 2H and 3R polytypes. In each case, molybdenum atoms occupy trigonal-prismatic sites within the layers. In addition, in the system MoS_2-xSe_x, a continuous series of solid solutions can be prepared, all having the same 2H two-layer hexagonal structure (space group P6₃/mmc). We report in this communication the evolution of lattice parameters of the mixed-anion system.