Raman characteristic peaks induced by the topological defects of carbon nanotube intramolecular junctions

The vibrational modes of some single-wall carbon nanotube (SWNT) intramolecular junctions (IMJs) have been calculated using the latest Brenner reactive empirical bond order (REBO) potential, based on which their nonresonant Raman spectra have been further calculated using the empirical bond polarizability model. It is found that the Raman peaks induced by pentagon defects lie out of the G-band of the SWNTs; thus, the high-frequency part of the Raman spectra of the SWNT IMJs can be used to experimentally determine their detailed geometrical structures. Also, the intensity of the Raman spectra has a close relation with the number of pentagon defects in the SWNT IMJs. Following the Descartes-Euler polyhedral formula, the number of heptagon defects in the SWNT IMJs can also be determined. The first-principles calculations are also performed, verifying the results obtained by the REBO potential. The G band width of the SWNT IMJ can reflect the length of its transition region between the pentagon and heptagon rings.