Equation of state of cubic hafnium(IV) nitride having Th3P4 -type structure

Pressure dependence of the specific volume, V(P)V(P), of the recently discovered high-pressure compound Hf3N4 having cubic Th3P4-type structure (c- Hf3N4) has been measured at room temperature up to 43.9 GPa in a diamond anvil cell using energy-dispersive X-ray powder diffraction combined with synchrotron radiation. A least-square fit of the Birch–Murnaghan equation of state to the experimental V(P)V(P)-data yielded for c- Hf3N4 the bulk modulus of B0=227(7)GPa and its first pressure derivative of B0′=5.3(6). For B0′ fixed at 4 the bulk modulus of c- Hf3N4 was determined to be B0=241(2)GPa. The obtained B0B0-value is only insignificantly below that estimated in preliminary measurements. Existing theoretical predictions for B0B0 scatter around the present experimental data. The observation of a high bulk modulus of c- Hf3N4 supports the suggestion that this compound could have high hardness.