The thermodynamic properties of the new B-N phases were calculated from the phonon frequencies using the statistical thermodynamic approach on a high-precision sampling mesh in the Brillouin zone. The temperature dependencies of the heat capacity at constant volume (C V ) for all new boron nitrides are presented in Fig. ; for B 3 N 3 in comparison with the available experimental C p data for cubic BN . The heat capacity of tetragonal B 2 N 3 is slightly higher than that of the hexagonal phase (Fig. ), while the opposite is observed for B 3 N 3 (Fig. ). The heat capacities of both B 3 N 3 polymorphs are slightly higher than that of cubic BN, which is consistent with their more open structures compared to the dense cubic structure. The observed excellent agreement between the calculated and experimental data for cBN supports the validity of the method used to estimate the thermodynamic properties of new boron nitrides.