  We have studied by means of high-pressure x-ray diffraction the structural
stability of Ni2Mo3N, Co3Mo3N, and Fe3Mo3N. We also report ab initio computing
modeling of the high-pressure properties of these compounds, Pd2Mo3N, and
Pt2Mo3N. 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 like gamma-Si3N4
