We have studied by means of high-pressure x-ray diffraction the structural stability of ${\text{Ni}}_2{\text{Mo}}_3\text{N}$, ${\text{Co}}_3{\text{Mo}}_3\text{N}$, and ${\text{Fe}}_3{\text{Mo}}_3\text{N}$. We also report ab initio computing modeling of the high-pressure properties of these compounds, ${\text{Pd}}_2{\text{Mo}}_3\text{N}$ and ${\text{Pt}}_2{\text{Mo}}_3\text{N}$. We have found that the nitrides remain stable in the ambient-pressure cubic structure at least up to 50 GPa and determined their equation of state. All of them have a bulk modulus larger than 300 GPa. Single-crystal elastic constants have been calculated in order to quantify the stiffness of the investigated nitrides. We found that they should have a Vickers hardness similar to that of cubic spinel nitrides such as $\gamma {\text{-Si}}_3{\text{N}}_4$.

• Received 15 September 2010

DOI:https://doi.org/10.1103/PhysRevB.82.174105