The dynamic stabilities were confirmed by the positive phonon magnitudes. The corresponding phonon band structures were obtained from a high resolution of the hexagonal Brillouin zone according to Togo et al. . Experimental specific heat C V data of diamond needed to assess the calculated results of the three 3D allotropes were obtained from Victor works . The electronic band structures were obtained using the all-electron DFT-based ASW method and the GGA exchange-correlation functional . The VESTA (Visualization for Electronic and Structural Analysis) program was used to visualize the crystal structures and charge densities.