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

Abstract

We report the far-infrared transmittance spectrum of a pure phase of the orthorhombic high-temperature and high-pressure C 60 polymer and compare the results with a previously published spectrum of the charged RbC 60 orthorhombic polymer. Assignments for both spectra are made with the aid of first-principles quantum molecular dynamics simulations of the two materials. We find that the striking spectral differences between the neutral and charged linear fullerene polymers can be fully accounted for by charge effects on the C 60 ball.

Infrared, Raman, and DFT Vibrational Spectroscopic Studies of C60F36 and C60F48

“…The increased computational demands were prohibitive for these molecules since the interpretation of the spectra of lower symmetrical compounds requires a more accurate prediction of vibrational frequencies and relative intensities than for the parent fullerenes. The use of smaller basis sets (such as 3-21G) with Hartree−Fock or density functional theory (DFT) methods, , as well as application of semiempirical methods either of MNDO- 22 or tight-binding types, ,,, resulted in computational data of sufficient accuracy to provide a qualitative understanding of the vibrational structure but did not allow peak-to-peak assignment of the whole set of experimental data. Taking advantage of the density fitting technique, which allows considerable acceleration of pure DFT computations, we have applied the PBE/TZ2P approach to interpret vibrational spectra of polymeric C 60 , , and bromo- 39 and chlorofullerenes. , The method was found to be quite accurate in predictions of the carbon cage vibrations, while the frequencies of C−Hal bending and stretching modes were underestimated.…”

“…Nevertheless, until very recently, application of vibrational spectroscopy in the fullerene chemistry was very limited; it suffered from the lack of theoretical background, since the required first-principle vibrational calculations were hardly feasible for molecules of such large size ( n (C) > 60). Reported examples included mainly vibrational analysis of the parent fullerenes C 60 , , C 70 , and C 84 , azafullerene, some endohedral metallofullerenes, − C 60 polymers, − and four exohedral derivatives, C 60 Br 24 , C 60 F 20 , C 60 Cl 6 , and C 60 Cl 30 . The B3LYP/6-31G* approach was successfully used to provide complete assignment of C 60 and C 70 vibrational spectra with reported deviations from experimental data of less than 5 cm -1 . , Computations of the IR spectra of two C 84 isomers at this level of theory have also shown qualitative agreement with experimental data .…”