High-pressure structure, decomposition, and superconductivity of MoS2

The high pressure structural and electronic evolution of bulk MoS2, an important transition metal layered dichalchogenide, is currently under active investigation, particularly in search of superconductivity. Recent theoretical and experimental work predicted and verified a 2H(c) -> 2H(a) layer sliding structural transition at 20 GPa and a band overlap semiconductor-semimetal transition in the same pressure range. The poorly metallic and nonsuperconducting 2H(a) structure is known to persist up to a pressure of 81 GPa, but properties at higher pressures remain experimentally unknown. Here we predict, with a first-principles evolutionary search, that major structural and electronic transformations should take place in equilibrium at higher pressures near 130-140 GPa. The main motif is a decomposition into MoS + S, also heralded in a small bimolecular cell by the appearance of a metastable nonlayered metallic MoS2 structure with space group P4/mmm. Unlike semimetallic 2H(a)-MoS2, the new high pressure phases are expected to be fully metallic and superconducting with higher critical temperatures than even alkali-intercalated MoS2.