Structural, electronic, elastic and superconducting properties of noble metal nitrides MN2 (MÂ =Â Ru, Rh, Pd)

The structural stability, electronic structure, elastic and superconducting properties of noble metal nitrides MN2 (M = Ru, Rh, Pd) are investigated in tetragonal (P4/mbm), fluorite (Fm3m), orthorhombic (Pnnm), pyrite (Pa-3) and hexagonal (P6/mmm) phases using first principles calculations. The calculated lattice parameters are in good agreement with other theoretical results. Among the considered structures, RhN2 and PdN2 are found to be most stable in tetragonal structure, whereas RuN2 is stable in fluorite structure. A sequence of structural phase transition is predicted under high pressure in these metal nitrides. The electronic structure reveals that these nitrides are metallic. These metal nitrides are found to be covalent, ionic and metallic in the stable phase. The observations show that these metal nitrides are mechanically stable at ambient condition. The superconducting transition temperatures for RuN2, RhN2 and PdN2 are found to be 1.65 K, 5.01 K and 8.7 K respectively.