From minimization of the calculated Gibbs free energy G (T, p) and the methodology described in section II, p-T phase diagrams were constructed to determine the relative thermodynamic stability of the BN polytypes, h-BN, r-BN, c-BN and w-BN. with increasing temperature seen from T = 300 K where the transformation from r-BN to c-BN takes place at p = 0.4 GPa, while the transition pressure increases to 5.7 GPa at T = 2400 K. From these calculations, it is evident that although considered, neither h-BN nor w-BN was found to be thermodynamically favored at the investigated temperatures and pressures.