Low-temperature heat capacity of fullerite C60 doped with nitrogen

Gurevich, A. M.; Terekhov, Alexander V.; Kondrashev, D. S.; Долбин, А. В.; Cassidy, David J.; Gadd, G. E.; Moricca, S.; Sundqvist, Bertil

doi:10.1063/1.2364490

“…The heat capacity of the interstitial solution (N 2 ) 0.2 C 60 was measured in the interval T = 2 -15 K using an adiabatic calorimeter [44]. It was found that the heat capacity of the solution was independent of the temperature prehistory of the sample.…”

Section: Introductionmentioning

confidence: 99%

Low-temperature heat capacity of fullerite C60 doped with deuteromethane

Bagatskii

¹

,

Sumarokov

²

,

Долбин

³

et al. 2012

Low Temperature Physics

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PostprintThis is the accepted version of a paper published in Low temperature physics (Woodbury, N.Y., Print). This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. Citation for the original published paper (version of record):Bagatskii, M., Sumarokov, V., Dolbin, A., Sundqvist, B. (2012) Low-temperature heat capacity of fullerite C-60 doped with deuteromethane.Low temperature physics (Woodbury, N.Y., Print) The heat capacity C of fullerite doped with deuteromethane (CD 4 ) 0.4 (C 60 ) has been investigated in the temperature interval 1.2 -120 K. The contribution 4 CD ΔC of the CD 4 molecules to the heat capacity C has been separated. It is shown that at T ≈ 120 K the rotational motion of CD 4 molecules in the octahedral cavities of the C 60 lattice is weakly hindered. As the temperature decreases to 80 K, the rotational motion of the CD 4 molecules changes from weakly hindered rotation to libration. In the range T = 1. Keywords:Heat capacity, fullerite С 60 , rotational dynamics of CD 4 IntroductionThe discovery of new forms of carbon (fullerite, carbon nanotubes, graphene) has attracted much interest from researchers working in different fields of physics, chemistry and materials science. The interest is first of all provoked by the wide-range diversity of the physical and chemical properties of these objects. A comprehensive investigation of the physical properties of these materials is of great importance for both fundamental science and practical applications.The thermal properties of pure fullerite have been investigated in numerous studies. Unfortunately, there have been few studies of the dynamics of impurities in C 60 crystals.In the low temperature phase there is one octahedral and two tetrahedral cavities for each C 60 molecule in the lattice. The average sizes of these are ≈ 4.12 Ǻ and ≈ 2.2 Ǻ, respectively [1,2]. Under certain conditions the octahedral cavities can be occupied by impurity atoms or molecules whose sizes are smaller than or similar to the size of the cavity. By now various experimental methods have been used to investigate fullerite C 60 doped with inert gas atoms [3][4][5][6][7][8] and simple molecules [9][10][11][12][13][14][15] of different symmetries and sizes. Doping affects significantly the physical properties of fullerite at low temperatures [16][17][18].The quantitative and qualitative features of the behavior of A x C 60 (A = 4 He, Ne, Ar, Kr, Xe) and M x C 60 (M = H 2 , N 2 , O 2 , CO, CH 4 , CD 4 ) systems depend in particular on the concentration x (x is the fraction of the octahedral cavities occupied by admixtures) and on the atomic / molecular parameters of the admixtures. Note that in a 4 He -C 60 solution the 4 He atoms can also occupy the tetrahedral cavities. The masses, the moments of inertia, the central and noncentral forces of the pair interaction of H 2 , N 2 , O 2 , CO, CH 4 and CD 4 molecules are much smaller than those of C 60 molecules. As a result, admixture of these molecules to fullerite ...

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“…Note that the data on the heat capacity of C 60 are essential for analyzing the heat capacities of new C 60 -containing nanomaterials, for example, elementary atomic and molecular gaseous substances that form interstitial solutions in the octahedral voids of fullerite C60 [39][40][41].…”

Section: Introductionmentioning

confidence: 99%

The low-temperature heat capacity of fullerite C60

Bagatskii

¹

,

Sumarokov

²

,

Barabashko

³

et al. 2015

Low Temperature Physics

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PostprintThis is the accepted version of a paper published in Low temperature physics (Woodbury, N.Y., Print). This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination.Citation for the original published paper (version of record):Bagatskii, M., Sumarokov, V., Barabashko, M., Dolbin, A V., Sundqvist, B. (2015) The low-temperature heat capacity of fullerite C 60 . Abstract:The heat capacity at constant pressure of fullerite C 60 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 C 60 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 C 60 is described by linear and cubic terms. The limiting Debye temperature at T → 0 K has been estimated (Θ 0 = 84.4 K). In the interval from 1.2 to 30 K the experimental curve of the heat capacity of C 60 describes the contributions of rotational tunnel levels, translational vibrations (in the Debye model with Θ 0 = 84.4 K), and librations (in the Einstein model with Θ E,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 hightemperature limit of translational vibrations (3 R) and the near-free rotational motion of C 60 molecules (1.5 R).

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