Neutron studies of vibrations in fullerenes

Pintschovius, L.

doi:10.1088/0034-4885/59/4/001

Cited by 52 publications

(46 citation statements)

References 74 publications

(78 reference statements)

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“…involve carbon displacements, Li ions being largely immobile, as seen from the weak Li participation factors in this energy range (see Fig.4 Li O and Li T ) and the Li partial density of states (pDOS) (see Fig.5). As already discussed for other polymeric forms of C 60 , these phonon modes share strong similarities with those of bulk C 60 , but the DOS spectrum also differs significantly in some places, which can be ascribed to the reduced symmetry of the polymeric cage and to the different nature of the hybridization of some C-C bonds at the cage surface [48][49][50] .…”

Section: Phonon Dispersion Curves and Phonon Dossupporting

confidence: 53%

Structure and dynamics of the fullerene polymerLi4C60studied with neutron scattering

et al. 2015

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The two-dimensional polymer structure and lattice dynamics of the superionic conductor Li 4 C 60 are investigated by neutron diffraction and spectroscopy. The peculiar bonding architecture of this compound is confirmed through the precise localisation of the carbon atoms involved in the intermolecular bonds. The spectral features of this phase are revealed through a combination of ab-initio lattice dynamics calculations and inelastic neutron scattering experiments. The neutron scattering observables are found to be in very good agreement with the simulations which predict a partial charge transfer from the Li atoms to the C 60 cage. The absence of a well defined band associated with the Li atoms in the experimental spectrum suggests that this species is not ordered even at the lowest temperatures. The calculations predict an unstable Li sublattice at a temperature of ∼ 200 K, that we relate to the large ionic diffusivity of this system: low frequency optic modes of the Li ions couple to the soft structure of the polymer.

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Section: Phonon Dispersion Curves and Phonon Dossupporting

confidence: 53%

Structure and dynamics of the fullerene polymerLi4C60studied with neutron scattering

et al. 2015

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“…Experimentally, the intermolecular frequencies fall in the range from zero and up to almost 7 meV. 31 We have used a value of ω ph = 1.8 meV which is substantially smaller than the average frequency of the experimental spectrum. The resulting λ ∼ 0.6 should therefore be substantially larger than the experimental value.…”

Section: Comparison Of Hi and Le Couplingmentioning

confidence: 99%

Electrical resistivity at large temperatures: Saturation and lack thereof

Calandra

Gunnarsson

2002

Phys. Rev. B

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Many transition metal compounds show a saturation of the electrical resistivity at high temperatures, T , while the alkali-doped fullerenes and the high-Tc cuprates are usually considered to show no saturation. We present a model of transition metal compounds, which shows saturation, and a model of alkali-doped fullerenes, which shows no saturation. The electron scattering is assumed to be due to interaction with phonons. The properties of these models are determined by performing quantum Monte-Carlo calculations. To analyze the results, as well as earlier results for the high-Tc cuprates, we use the f-sum rule. We demonstrate that the f-sum rule leads to a natural upper limit for the resistivity at large T . For some systems and at low T , the resistivity increases so rapidly that this upper limit is approached for experimentally accessible temperatures. The resistivity then saturates. For a model of transition metal compounds with weakly interacting electrons, the upper limit corresponds to an apparent mean free path consistent with the Ioffe-Regel condition. For a model of the high Tc cuprates with strongly interacting electrons, however, the upper limit is much larger than the Ioffe-Regel condition suggests. This upper limit is not exceeded by experimental resistivities. The experimental data for the cuprates are therefore consistent with saturation. After saturation the resistivity normally grows slowly. The alkali-doped fullerenes can be considered as systems where saturation has happened already for T = 0, due to orientational disorder. We show, however, that for these systems the resistivity grows so rapidly after "saturation" that this concept is meaningless. This is due both to the small band width and to the coupling to the level energies of the important (intramolecular) phonons in the fullerenes.

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“…D'autre modes ont un caractère mixte. Il est possible de déterminer expérimentalement le caractère de chacune de ces branches grâce à la dépendance en fonction du vecteur de diffusion de l'intensité de la fonction de diffusion associée à ce mode (voir [15] pour de plus amples détails). Il est aussi possible d'observer des phénomènes d'anticroisement entre les branches, ce qui traduit un couplage entre certains des modes inter-moléculaires.…”

Section: Excitations Inter-moléculaires Du C 60unclassified

“…On voit apparaître des lobes intenses situés à l'énergie E 2.5 meV et aux vecteurs de diffusion Q = 3.3 et 5.0 Å −1 . Ils correspondent aux maxima du facteur de forme associé aux mouvements de rotation de la molécule de C 60 [4,8,15,17]. Par la suite, on appellera souvent ce pic situé à environ 2.5 meV, "la" libration du C 60 .…”

Section: Excitations Inter-moléculaires Du C 60unclassified

“…Les courbes de dispersion se résument à 3 branches acoustiques, comme représenté sur la figure 11. Elles peuvent être modélisées de manière très correcte par un modèle simple, où chaque C 60 est assimilé à un atome de gaz noble en interaction avec les autres au moyen d'un tenseur de constantes de forces à 3 paramètres ajustables [13,15]. Il est remarquable de constater que l'augmentation du paramètre de maille causée par l'intercalation du cubane est plus faible que la dimension latérale de la molécule de cubane.…”

Section: Effet De La Transition Ordre/désordre Sur La Dynamique De Baunclassified

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Phonons et vibrations dans les fullerènes, les nanotubes de carbone et leurs composés

Cambedouzou

Rols

2010

JDN 16 – Diffusion Inélastique Des Neutrons Pour l'Etude Des Excitations Dans La Matiére Condensée

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Résumé. À travers quelques résultats expérimentaux marquants, nous illustrons l'apport des techniques de diffusion inélastique des neutrons à la compréhension des dynamiques de vibration et de réseau des fullerènes et des nanotubes de carbone. L'accent est particulièrement mis sur l'étude des excitations intra et inter-moléculaires des fullerènes de C 60 , ainsi que sur la transition dynamique ordre/désordre caractéristique de ces molécules. En outre, une part significative de ce chapitre est dédiée à divers composés d'intercalation et d'insertion des fullerènes et des nanotubes de carbone, comme le co-cristal "fullerène-cubane" formé d'un arrangement de molécules de formes sphérique et cubique, ou encore les composés appelés "peapods", dans lesquels des fullerènes C 60 sont insérés à l'intérieur de nanotubes de carbone monofeuillets.

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Neutron studies of vibrations in fullerenes

Cited by 52 publications

References 74 publications

Structure and dynamics of the fullerene polymerLi4C60studied with neutron scattering

Structure and dynamics of the fullerene polymerLi4C60studied with neutron scattering

Electrical resistivity at large temperatures: Saturation and lack thereof

Phonons et vibrations dans les fullerènes, les nanotubes de carbone et leurs composés

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