Besides the structural stability criteria observed for 'neoglitter' from the positive magnitudes of the elastic constants and their combinations, another stability criterion is obtained from the phonons. Fig. shows the phonon bands. Along the horizontal direction, the bands run along the main lines of the tetragonal Brillouin zone (reciprocal k-space). The vertical direction shows the frequencies given in units of terahertz (THz). Since no negative frequency magnitudes are observed, tet-C 6 is considered as dynamically stable. There are 3N-3 optical modes at higher energy than three acoustic modes that can be counted between  and R. They start from zero energy (ω = 0) at the  point, center of the Brillouin zone, up to a few terahertz. Acoustic modes describe the lattice rigid translation modes with two transverse modes and one longitudinal mode. The remaining bands correspond to the optic modes culminating at ω = 40 THz, a magnitude close to the observed for diamond by Raman spectroscopy: ω ~ 40 THz .