Potential super-hard Osmium di-nitride with fluorite structure: First-principles calculations

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We have performed systematic first-principles calculations on di-carbide, -nitride, -oxide and -boride of platinum and osmium with the fluorite structure. It is found that only PtN₂, OsN₂ and OsO₂ are mechanically stable. In particular OsN₂ has the highest bulk modulus of 360.7 GPa. Both the band structure and density of states show that the new phase of OsN₂ is metallic. The high bulk modulus is owing to the strong covalent bonding between Os 5d and N 2p states and the dense packed fluorite structure.