Figure 2.

Phonon band structure of diamond-structured carbon as calculated from the PROPhet potential (black lines) and density functional perturbation theory (red circles). Phonons with the PROPhet potential were computed within the frozen-phonon approximation using a 6 × 6 × 6 supercell, while those from DFPT were computed within VASP using a primitive cell. All band structures were interpolated using the phonopy⁴³ code. These results are in good agreement with experimental and other theoretical results^{44, 45}.