To verify the dynamic stability of the novel carbon allotrope, an analysis of the phonon properties was performed. Phonons are quanta of vibrations with frequency ω and energy proportional to the h Planck constant. For C 20 and C 8 the phonon band structures obtained from a high resolution of the tetragonal and cubic Brillouin zones BZ are shown in Figure , in accordance with the method proposed by Togo et al. . In the two panels the bands (red lines) develop along the main directions of the respective BZ (horizontal x-axis), separated by vertical lines for better visualization. The vertical direction (y-axis) represents the frequencies ω, given in terahertz (THz).