Structural Phase Transitions in the Fullerene C<sub>60</sub>
W. I. F. David; R. M. Ibberson; T. J. S. Dennis; J. P. Hare; K. Prassides
Журнал:
EPL (Europhysics Letters)
Дата:
1992-02-21
Аннотация:
High-resolution powder neutron diffraction has been used to study the crystal structure of the fullerence C<sub>60</sub> in the temperature range 5 K to 320 K. Solid C<sub>60</sub> adopts a cubic structure at all temperatures. The experimental data provide clear evidence of a continuous phase transition at ca. 90 K and confirm the existence of a first-order phase transition at 260 K. In the high-temperature face-centred-cubic phase (T > 260 K), the C<sub>60</sub> molecules are completely orientationally disordered, undergoing continuous reorientation. Below 260 K, interpretation of the diffraction data is consistent with uniaxial jump reorientation principally about a single ⟨111⟩ direction. In the lowest-temperature phase (T < 90 K), rotational motion is frozen although a small amount of static disorder still persists.
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