The electronic band structures shown in Fig. were obtained using the ASW method with crystal inputs of the calculated crystal parameters from Table . The bands develop along the main directions of the primitive rhombohedral Brillouin zone. For the diamond-like 9R C 18 , Fig. shows an insulating behavior with a large band gap ~5eV separating the filled valence band VB from the empty conduction band CB. The energy level along the vertical line is with respect to the top of the valence band (VB), E V . In contrast, ene-C 21 is metallic-like with a band that crosses the Fermi level E F , and the energy is now with respect to E F . Such behavior can be explained by the delocalized nature of the π electrons resulting from the C=C bonds. Finally, yne-C 24 , shows a semiconducting behavior and the zero energy is with respect to E V . The localization of the charge at the triple CC bond can explain the semiconducting behavior.