Structural, electronic and elastic properties of noble metal sub-nitrides M2N (M=Ru, Rh, Pd)

Abstract Ab initio calculations are performed to investigate the structural stability, electronic structure and elastic properties of noble metal sub-nitrides M2N (M = Ru, Rh, Pd). The metal nitrides, Ru2N and Rh2N are found to be stable in anti-fluorite structure, whereas Pd2N is stable in tetragonal structure. In Ru2N and Rh2N, structural phase transition is predicted from antifluorite to orthorhombic phase whereas tetragonal to antifluorite and then antifluorite to pyrite phase transitions are predicted in Pd2N under high pressure. The electronic structure reveals that these nitrides are metallic. The calculated elastic constants indicate that these materials are mechanically stable at ambient condition. The Debye temperature values are reported for all the phases of these nitrides. The high bulk modulus indicates that these materials are super hard materials. They are ductile in nature at normal and high pressures. The bonding nature of these materials is found to be a mixture of covalent, metallic and ionic attribution at ambient condition.