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 K-0 = 274 +/- 3 GPa when fixing K-0(1) = 4. This value agrees well with the value obtained from the first-principles numerical calculations. (C) 2007 Elsevier Ltd. All riahts reserved.