Marcasite osmium nitride with high bulk modulus: First-principles calculations

The authors propose marcasite $OsN2$ as a structure of the experimentally synthesized orthorhombic $OsN2$ compound. From the first-principles calculations, they find that the marcasite structure is more stable than the fluorite and pyrite ones and its lattice constants are in good agreement with the experiment. The calculated elastic constants for marcasite $OsN2$ satisfy the stability condition. The band structure shows that marcasite $OsN2$ is metallic. There is a pseudogap around the Fermi level of the total density of states of marcasite $OsN2$⁠, which may contribute to its stability. The appearance of the pseudogap is mainly caused by the anisotropic connectivity of $OsN6$ octahedra.