Does the real ReN2 have the MoS2 structure?

Rhenium nitride (ReN2) with the hexagonal MoS2 structure was recently synthesized by metathesis reaction under high pressure. Here the calculated elastic and thermodynamic stabilities and chemical bonding show that the MoS2 phase is unstable based on first-principles calculations. Meanwhile, the MoS2-type ReN2 compound may be stabilized by nitrogen-vacancies from X-ray diffraction and supercell calculations. Structure searches identify a monoclinic C2/m phase for ReN2, which is energetically more stable than previous predictions and MoS2 structure over a wide range of pressures. Above 130 GPa, a tetragonal P4/mbm phase becomes favorable from enthalpy calculations. Both phases have superior mechanical properties, and their syntheses would have important applications fundamentally and technologically.