Thermal expansion of deuterium methane solutions in fullerite C60 at low temperatures. Isotopic effect
A.V. Dolbin, N.A. Vinnikov, V.G. Gavrilko, V.B. Esel'son, V.G. Manzhelii
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
G.E. Gadd, S. Moricca, and D. Cassidy
Australian Nuclear Science & Technology Organisation, NSW 2234, Australia
Department of Physics, Umea University, SE - 901 87 Umea, Sweden
Received December 1, 2008, revised December 8, 2008
The thermal expansion of CD4 solutions in an oriented glass C60 with the molar CD4 concentrations
20 and 50% has been investigated in the interval 2.5–23 K. At T = 4.5–5.5 K the orientational CD4–C60 glass undergoes a first-order phase transition,
which is evident as a hysteresis of the linear thermal expansion coefficient a, as well as maxima in the temperature dependences a(T) and t1(T), where t1 is the characteristic time of thermalization of the samples. The characteristic times of C60
molecule reorientation and the phase transformations in the solutions have been estimated. The results obtained are compared with the corresponding
data taken on the CH4–C60 solution. The conclusion can be drawn about a tunnel rotation of CH4
and CD4 molecules in the octahedral interstitial sites of the C60 lattice.
PACS: 65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.; PACS: 74.70.Wz Fullerenes and related materials.