Theoretical Studies of Raman Spectra for Planar Polymerized C60

Abstract

We have used an approximate first-principles method together with a bond-polarizability model to calculate theoretical Raman spectra for the orthorhombic (O), tetragonal (T), and rhombohedral (R) phases of pressure-polymerized C 60 solid. We have also calculated Raman spectra for a sequence of C 60 polymer structures which include all possible two-connected C 60 balls, to help elucidate the yet unknown structure of the room-temperature C 60 photopolymer. To quantitatively determine the contribution of the I h C 60 vibrational modes to each polymer mode, we have expanded the polymer eigenvectors in the eigenvectors of I h C 60 . Our calculated O-polymer Raman spectrum is compared with the available experimental spectrum measured under off-resonance conditions. For the sequence of two-connected-ball polymers, we present our calculated spectra in the frequency region of the I h C 60 A g (2) vibrational mode, and relate these spectra to measured spectra for the room-temperature photopolymer. We find the simplest agreement with experiment for the triangular C 60 trimer.

New features in the pressure dependence of photoluminescence spectra of C60 at room temperature

“…These values are in excellent agreement with theoretical and experimental results for pristine C 60 [20,21]. Here, we have combined Raman shifts for the A g (2) band from our recent measurements [6] and from the measurements of the Raman spectra at selected pressures during the PL experiments.…”

Far-infrared vibrational properties of linearC60polymers: A comparison between neutral and charged materials

“…1͑d͔͒; it has been proposed as the principal component of the C 60 photopolymer. 36,41 Figure 3 displays the far-IR spectrum of the O polymer at 10 K. The experimental peak frequencies in Fig. 3 are assigned to IR-active O-polymer vibrational modes based upon a comparison with our QMD calculations.…”

New Polymeric Phase in Low‐Doped Lithium Intercalated Fullerides

“…The rather complex Raman spectrum, shown in Figure 5, strongly suggests that the distortion of the C 60 cage has already lifted the degeneracy of the H g modes, while the narrow peaks confirm the insulating nature of the compound. Another important feature supporting the polymerisation is the presence of a peak at 980 cm 21 : this resonance is commonly associated with the stretching mode of the four-membered carbon ring involved in the intermolecular bonds and has been always observed in the [2 þ 2] cycloaddicted polymers (12).…”