b) Dynamical stabilities from the phonons Further stability criteria can be obtained from the phonon dispersion relations in the Brillouin zone, i.e. the phonon dispersions. Following the method presented in the 'Computational framework' section, the obtained phonon dispersion curves for C 6 , B 2 C 4 and B 2 C 2 N 2 are shown in Fig. . The bands span the main lines of the tetragonal BZ.