Pressure effects on the phase stability of cubic BNC ternary alloys

Pressure effects on the phase stability of cubic BNC alloys were examined by Monte Carlo simulations and the cluster expansion technique based on first-principles calculations. At pressure P = 10GPa, solution energy of neighboring B-N and C-C atoms into diamond and cubic BN are both higher than those at P = 0 GPa, indicating a decrease of solubility in c-BNC under applied pressure. Monte Carlo statistical simulation reveal that the applied pressure decreases solubility limits by almost half of those at P = 0 GPa. This significant decrease can mainly be attributed to the increase of volume with the formation of a c-BNC solid solution. Formation of neighboring B-N bonds decreases volume, while that of second-neighboring B-N increases volume for c-BNC, which naturally increases the stability of c-BN and diamond in the c-BNC solid solution under external pressure.