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

Pressure dependence of the specific volume, 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 ) -data yielded for c- Hf3N4 the bulk modulus of B 0 = 227 ( 7 ) GPa and its first pressure derivative of B 0 ′ = 5.3 ( 6 ) . For B 0 ′ fixed at 4 the bulk modulus of c- Hf3N4 was determined to be B 0 = 241 ( 2 ) GPa . The obtained B 0 -value is only insignificantly below that estimated in preliminary measurements. Existing theoretical predictions for B 0 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.