First principles investigation of structural, electronic and optical properties of synthesized radiaannulene oligomers for 6,6,12-graphyne

6,6,12-graphyne is the first non-hexagonal lattice that evinced graphene like Dirac fermions. The oligomers of this fascinating carbon system have recently been synthesized via iterative acetylenic coupling reactions. In this work, we have critically explored the characterizing Raman spectra, electronic and optical properties of these synthesized compounds from a theoretical perspective. The experimental yield of the oligomers shows an excellent agreement with our evaluated cohesive energy/atom. Besides, the first principles Raman spectra possess the signatures of both sp(2) and sp hybridized carbon atoms present in the systems. The degree of polymerization of the oligomers can also be efficiently determined from the Raman active modes. Furthermore, the systems exhibit strong optical responses in the visible range. The limit above which these subsystems mimic the optical properties of the corresponding nanoribbon has been revealed. Finally, the UV-vis absorption spectra and non-linear hyper-polarizability have been reported in connection with the electronic structure for all the oligomers. The band gaps and corresponding optical responses in the visible range establish the relevance of these oligomers in smart optoelectronic devices. This work provides a thorough comparison between the already synthesized oligomers of 6,6,12-graphyne to assist future experiments and applications.

Automated summary

This study explores the Raman spectra, electronic, and optical properties of 6,6,12-graphyne oligomers from a theoretical perspective. The experimental yield of the oligomers aligns well with evaluated cohesive energy/atom, and the Raman spectra exhibit signatures of both sp(2) and sp hybridized carbon atoms. The degree of polymerization of the oligomers can be efficiently determined from the Raman active modes, indicating strong optical responses in the visible range and relevance in optoelectronic devices.