The low-temperature heat capacity of fullerite C₆₀

• Veröffentlicht in: Физика низких температур
• Datum: 2015
• Hauptverfasser: Bagatskii, M.I., Sumarokov, V.V., Barabashko, M.S., Dolbin, A.V., Sundqvist, B.
• Format: Artikel
• Sprache: English
• Veröffentlicht: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2015
• Schlagworte: Наноструктуры при низких температурах
• Online Zugang: https://nasplib.isofts.kiev.ua/handle/123456789/127965
• Назва журналу: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Zitieren: The low-temperature heat capacity of fullerite C₆₀ / М.I. Bagatskii, V.V. Sumarokov, M.S. Barabashko, A.V. Dolbin, B. Sundqvist// Физика низких температур. — 2015. — Т. 41, № 8. — С. 812–819. — Бібліогр.: 54 назв. — англ.

The heat capacity at constant pressure of fullerite C₆₀ has been investigated using an adiabatic calorimeter in a temperature range from 1.2 to 120 K. Our results and literature data have been analyzed in a temperature interval from 0.2 to 300 K. The contributions of the intramolecular and lattice vibrations into the heat capacity of C₆₀ have been separated. The contribution of the intramolecular vibration becomes significant above 50 K. Below 2.3 K the experimental temperature dependence of the heat capacity of C60 is described by the linear and cubic terms. The limiting Debye temperature at T → 0 K has been estimated (Θ0 = 84.4 K). In the interval from 1.2 to 30 K the experimental curve of the heat capacity of C₆₀ describes the contributions of rotational tunnel levels, translational vibrations (in the Debye model with Θ0 = 84.4 K), and librations (in the Einstein model with ΘE,lib = 32.5 K). It is shown that the experimental temperature dependences of heat capacity and thermal expansion are proportional in the region from 5 to 60 K. The contribution of the cooperative processes of orientational disordering becomes appreciable above 180 K. In the high-temperature phase the lattice heat capacity at constant volume is close to 4.5 R, which corresponds to the high-temperature limit of translational vibrations (3 R) and the near-free rotational motion of C60 molecules (1.5 R).