Compression behavior of NbC under nonhydrostatic conditions to 57 GPa

The analysis of the diffraction data under nonhydrostatic stress condition created in a diamond anvil cell suggests that the compressive strength of NbC crystallites is at least 24 ± 4 GPa at a confining pressure of 57 ± 0.5 GPa. When using Al as a pressure transmitting medium in the diamond anvil cell pressure conditions become nearly hydrostatic. The bulk modulus derived from the compression data under quasi-hydrostatic pressure condition gives K0 = 274 ± 3 GPa when fixing K0′=4. This value agrees well with the value obtained from the first-principles numerical calculations.