Low temperature heat capacity and lattice dynamics of C70

Tanaka, Toshiaki; Ataké, Tooru

doi:10.1016/0022-3697(95)00283-9

Cited by 13 publications

(9 citation statements)

References 27 publications

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“…The calculated entropy changes (dividing the reported enthalpy change by the transition temperature) are approximately 9 and 5 J/(mol K), respectively. Tanaka and Atake, studying highly purified C 70 , found the two transitions at 280 and 340 K using DSC and determined the enthalpy change of the lower-temperature transition to be 1700 J/mol using microcalorimetry, with the corresponding entropy change given as 4.7 J/(mol K). They estimated the enthalpy change of the higher-temperature transition to be comparable, based on the DSC trace.…”

Section: Resultsmentioning

confidence: 99%

“…Calorimetric studies provide important insight into the nature of the rotation and libration of the fullerene molecules in fullerene-based solids − and thus reveal the strength of the interactions among fullerenes, dopants, and guest species. The temperature, enthalpy, and entropy of the phase transitions all reflect the molecular interactions.…”

Section: Introductionmentioning

confidence: 99%

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Orientational Ordering and Low-Temperature Libration in the Rotor−Stator Cocrystals of Fullerenes and Cubane

et al. 2009

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Cocrystals of cubane and fullerenes, C60-cubane and C70-cubane, show distinct rotational ordering transitions. We studied the corresponding structural changes with temperature-dependent X-ray diffraction and the thermodynamics of the phase transitions with adiabatic microcalorimetry and differential scanning calorimetry. C60-cubane has one phase transition around 130 K from a high-temperature fcc phase with freely rotating C60 to a low-temperature orthorombic phase in which the fullerene rotation is frozen. The corresponding enthalpy change is approximately 1170 J/mol, and the entropy change is 9.6 J/(mol K). C70-cubane has two phase transitions. Around 380 K, the high-temperature fcc phase with freely rotating C70 transforms into a bct phase in which the C70 rotates uniaxially around an axis that precesses around the c direction with a full opening angle of 40 degree. Around 170 K, the uniaxial rotation also freezes out, with an accompanying structural transition to monoclinic and enthalpy and entropy changes of 620 J/mol and 8.7 J/(mol K), respectively. The low-temperature specific heat was analyzed in terms of the Debye-Einstein model to estimate the librational energies of the fullerenes and Debye temperatures. We found very similar values for the two cocrystals, approximately Elib = 2.2 meV and TDebye = 23 K. For reference, we also measured the specific heats of pure C60 and C70 and found Elib = 2.96 meV and TDebye = 32 K for C60 and Elib = 1.9 meV and TDebye = 20 K for C70.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Orientational Ordering and Low-Temperature Libration in the Rotor−Stator Cocrystals of Fullerenes and Cubane

et al. 2009

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“…Various computational approaches, from the Debye models with adjustable parameters 22,56 to those based on the examination 81,67 and integration 53,82 of phonon spectra of crystals may give a key to a more comprehensive interpretation of the heat capacities of fullerenes in the condensed state. Both theoretical 83 ± 87 and experimental 88,89 data on the fullerene lattice vibrations can be found in the literature.…”

Section: Enthalpies Of Formation Of C 60 and C 70mentioning

confidence: 99%

Thermodynamic properties of C₆₀and C₇₀fullerenes

Diky¹,

Kabo²

2000

Russ. Chem. Rev.

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The most reliable values of the basic thermodynamic The most reliable values of the basic thermodynamic parameters of the C parameters of the C 60 60 and C and C 70 70 fullerenes are recommended based fullerenes are recommended based on the analysis of the published data and original calculations, on the analysis of the published data and original calculations, viz viz., enthalpies of formation in the solid and gaseous states,., enthalpies of formation in the solid and gaseous states, saturated vapour pressures, enthalpies of sublimation, enthalpies saturated vapour pressures, enthalpies of sublimation, enthalpies of phase transitions, heat capacities, entropies in the condensed of phase transitions, heat capacities, entropies in the condensed state and heat capacities and entropies in the ideal gas state. The state and heat capacities and entropies in the ideal gas state. The factors influencing the results of thermodynamic studies of full-factors influencing the results of thermodynamic studies of fullerenes are discussed. Various aspects of crystal structure determi-erenes are discussed. Various aspects of crystal structure determination, PVT-relationships and frequencies of normal modes of the nation, PVT-relationships and frequencies of normal modes of the C C 60 60 and C and C 70 70 fullerenes are considered in order to interpret and fullerenes are considered in order to interpret and correlate the thermodynamic data and extend them to a wide correlate the thermodynamic data and extend them to a wide temperature range. The bibliography includes 135 references. temperature range. The bibliography includes 135 references.

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“…A glass transition was observed due to molecular orientation in C 60 crystal [92]. The lattice dynamics calculation and molecular dynamics simulation have been used extensively to analyze the mechanism of molecular motion in the crystal [93,94]. Thermodynamic studies have been extended to various complex compounds [95].…”

Section: Critical Problems Solved By Calorimetry and Thermodynamicsmentioning

confidence: 99%

Low temperature heat capacity and lattice dynamics of C70

Cited by 13 publications

References 27 publications

Orientational Ordering and Low-Temperature Libration in the Rotor−Stator Cocrystals of Fullerenes and Cubane

Orientational Ordering and Low-Temperature Libration in the Rotor−Stator Cocrystals of Fullerenes and Cubane

Thermodynamic properties of C₆₀and C₇₀fullerenes

Application of calorimetry and thermodynamics to critical problems in materials science

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Low temperature heat capacity and lattice dynamics of C70

Cited by 13 publications

References 27 publications

Orientational Ordering and Low-Temperature Libration in the Rotor−Stator Cocrystals of Fullerenes and Cubane

Orientational Ordering and Low-Temperature Libration in the Rotor−Stator Cocrystals of Fullerenes and Cubane

Thermodynamic properties of C60and C70fullerenes

Application of calorimetry and thermodynamics to critical problems in materials science

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Thermodynamic properties of C₆₀and C₇₀fullerenes