In situ infrared spectroscopic and density-functional studies of the cross-linked structure of one-dimensional C60 polymer

We have examined the infrared (IR) spectra of electron-beam (EB) irradiated C60 films, using in situ IR spectroscopy in the temperature range of 60–300 K. The irradiation-time evolution of the IR spectra shows that two highly intense new peaks finally appear around 565 and 1340 cm−1 when the EB-induced C60 polymerization was saturated. To determine the cross-linked structure of the polymer explicitly, we have compared the IR spectra with theoretical spectra obtained from the cross-linked structure of all C120 stable isomers derived from the general Stone–Wales (GSW) rearrangement, using first-principles density-functional calculations. Since each C120 isomer has the same cross-linked structure as that of its corresponding one-dimensional (1D) C60 polymer, the IR modes obtained from the cross-linked structure of C120 are close to those obtained from the corresponding 1D polymer. Comparison between the experimental and theoretical IR spectra suggests that the 1D peanut-shaped C60 polymer has a cross-linked structure roughly similar to that of the P08 peanut-shaped C120 isomer.