Compressibility and structural stability of ultra-incompressible bimetallic interstitial carbides and nitrides

Abstract

We have investigated by means of high-pressure x-ray diffraction the structural stability of Pd${}_{2}$Mo${}_{3}$N, Ni${}_{2}$Mo${}_{3}$C${}_{0.52}$N${}_{0.48}$, Co${}_{3}$Mo${}_{3}$C${}_{0.62}$N${}_{0.38}$, and Fe${}_{3}$Mo${}_{3}$C. We have found that they remain stable in their ambient-pressure cubic phase at least up to 48 GPa. All of them have a bulk modulus larger than 330 GPa, the least compressible material being Fe${}_{3}$Mo${}_{3}$C, ${B}_{0}$ $=$ 374(3) GPa. In addition, apparently a reduction of compressibility is detected as the carbon content is increased. The equation of state for each material is determined. A comparison with other refractory materials indicates that interstitial nitrides and carbides behave as ultra-incompressible materials.