Does the real ReN2 have the MoS2 structure?

Abstract

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.