Computational studies on C36 and its dimer

The energetics of three competing low-energy isomers of C36 (D6h, D2d and C2v forms) in their singlet and triplet states were computed at the AM1, HF/3-21G, HF/6-31G∗ and B3LYP/6-31G∗ levels. The most stable structure is predicted to be the D6h isomer with a triplet ground state of 3A2u symmetry. This electronic structure can account for the `covalentʹ interactions noted in solid C36. The dimeric structure with D2h symmetry was optimized using the AM1 and HF/3-21G methods. Dimerization is calculated to be energetically favorable. Important changes expected due to dimerization in the vibrational and electronic spectra are pointed out.