Potential super-hard Osmium di-nitride with fluorite structure:   First-principles calculations
  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 PtN$_{2}$, OsN$_{2}$ and OsO$_{2}$ are mechanically stable. In particular OsN$_{2}$ has the highest bulk modulus of 360.7 GPa. Both the band structure and density of states show that the new phase of OsN$_{2}$ is metallic. The high bulk modulus is owing to the strong covalent bonding between Os 5\textit{d} and N 2\textit{p} states and the dense packed fluorite structure. 
Chang-Zeng Fan, Song-Yan Zeng, Li-Xin Li, Ri-Ping Liu, Wen-Kui Wang,   Ping Zhang, Yu-Gui Yao