Low temperature x-ray diffraction study of the phases of C70

Janaki, J.; Rao, G. Venugopal; Sastry, V. Sankara; Hariharan, Y.; Radhakrishnan, T. S.; Sundar, C. S.; Bharati, Ashok Kumar; Valsakumar, M. C.; Subramanian, N.

doi:10.1016/0038-1098(94)00907-4

Cited by 15 publications

(5 citation statements)

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“…It should be noted that most of observed phases were obtained during cooling of crystals that were grown at high-temperature conditions. The only monoclinic and hcpII phases were reported to be grown at room temperature but under conditions far from equilibrium.…”

Section: Intoductionmentioning

confidence: 99%

Dielectric Properties of C₇₀-Solvate Crystals Grown from a Benzene Solution

et al. 1998

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C 70 crystals with size up to 3 × 3 × 0.2 mm were grown from benzene solution. The real and imaginary parts of the complex conductivity of this crystals were studied in the frequency range 20 Hz-1 MHz and the temperature range from 10 K to the room temperature. The temperature dependence of the real and imaginary parts of conductivity showed two frequency-independent anomalies at 150 and 275 K. These anomalies are interpreted as phase transitions.

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Section: Intoductionmentioning

confidence: 99%

Dielectric Properties of C₇₀-Solvate Crystals Grown from a Benzene Solution

et al. 1998

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“…However, a large variety of contradictory experimental observations have been reported in the literature and there is no complete agreement so far. For example, some authors have reported only one transition [14,15], three transitions [16,17], or even a continuous transformation from hcp to monoclinic structure at slow cooling rates [18], while others have observed retention of the hcp structure down to 10 K in solution-grown samples [19]. The underlying cause of disagreement (impurity effects excluded) appears to be the manifestation of coexisting cubic and hexagonal phases in relative amounts that depend critically on the conditions of preparation, of observation and on thermal history of the samples.…”

Section: Introductionmentioning

confidence: 97%

Evolution of molecular ordering and phase transitions in C₆₀/C₇₀solid solutions

Rueda-Morales

Ortíz-López

2004

Physica Status Solidi (b)

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Polycrystalline solid solutions (C 60 ) x :(C 70 ) 1-x with 0 ≤ x ≤ 1 grown by sublimation are studied with AC calorimetry in the 5−300 K temperature range and with X-ray powder diffraction at room temperature. For concentrations 0.15 ≤ x ≤ 0.68, an hexagonal disordered (hcp) single phase is found at room temperature with no evidence of phase transitions occurring down to 5 K. This is indication of complete C 60 /C 70 miscibility and of freezing of orientational disorder at low temperature for this concentration range. Phase transitions below room temperature are detected only for concentrations close to the pure fullerenes, with critical temperatures decreasing as x departs away from x = 0 and 1. The elastic dipole model is applied in pure C 70 and C 70 -rich solid solutions to account for elastic interactions and ferroelastic ordering of the elongated C 70 molecule. Within this model, the evolution of ferroelastic phase transitions in C 70 -rich solid solutions is obtained and compared with available experimental data.

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“…For the former, the encapsulated metals include alkali-earth atoms (Ca, Sr, Ba) and lanthanide atoms (Sm, Eu, Tm, and Yb), 23,24 while for the latter, the encapsulated metals include Sc, Y, and lanthanide atoms, except for Sm, Eu, Tm, and Yb. [25][26][27] To date, the experimentally available empty fullerene molecules of a medium size (C 2n , 60 # 2n # 80) include C 60 , 28 C 70 , 29 C 76 , 30 C 78 , 30 and C 80 . 31,32 Interestingly, the C 72 , C 74 , and C 80 molecules were called ''missing fullerenes", 33 which are difficult to synthesize or isolate because of their structural instabilities or high chemical reactivity.…”

Section: Introductionmentioning

confidence: 99%