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Potential superhard osmium dinitride with fluorite and pyrite structure: First-principles calculations

2006; American Physical Society; Volume: 74; Issue: 12 Linguagem: Inglês

10.1103/physrevb.74.125118

1550-235X

Changzeng Fan, Zeng Song-yan, Lixin Li, Zhan Zai-Ji, Riping Liu, Wenkui Wang, Ping Zhang, Yugui Yao,

MXene and MAX Phase Materials

We have performed systematic first-principles calculations on dicarbide, -nitride, -oxide, and -boride of platinum and osmium with the fluorite structure. It is found that only $\mathrm{Pt}{\mathrm{N}}_{2}$, $\mathrm{Os}{\mathrm{N}}_{2}$, and $\mathrm{Os}{\mathrm{O}}_{2}$ are mechanically stable. In particular, $\mathrm{Os}{\mathrm{N}}_{2}$ has the highest bulk modulus of $360.7\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. Both the band structure and density of states show that the new phase of $\mathrm{Os}{\mathrm{N}}_{2}$ 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. In addition, the total-energy calculation for pyrite structure has also been performed, which indicates its mechanical and energetic stability but much lower bulk modulus compared to the fluorite structure.