Investigation of hardness in transition metal hexa-nitrides in cubic structure: A first-principles study

We have studied all 29 transition metal nitrides (TMNs) of stoichiometric ratio 1:6 (M:N) in cubic structure (space group: Im3m) using density functional theory-based calculations. Our calculations include computations of structural, mechanical, vibrational, magnetic, energetic, thermal, and electronic properties. Our calculations indicate that only 5 MN6 compounds are both vibrationally and mechanically stable. Out of them, the hardest compound CrN6 has Vickers hardness of 16 GPa. Higher hardness is directly proportional to higher mass density of the MN6, whereas inversely proportional to M-M and M -N bond lengths. The band structure analysis shows that all the mechanically stable compounds except HgN6 are metallic in nature. The study of magnetic properties reveals that only 8 of MN6 have magnetic moment.

Automated summary

We have studied the properties of 29 transition metal nitrides using density functional theory calculations. Only 5 compounds were found to be both vibrationally and mechanically stable, with CrN6 having the highest Vickers hardness. The hardness is directly proportional to mass density and inversely proportional to M-M and M-N bond lengths. The band structure analysis showed that all stable compounds except HgN6 are metallic in nature. Magnetic properties were found in only 8 compounds.