2014/06/23 by M. I. Bagatskiı̆, M. I. Bagatskii, Bagatskii, M. I. +13
Chemistry · Pharmacology, Toxicology and Pharmaceutics · Physics and Astronomy · #Chemical Reactions and Isotopes #FOS: Physical sciences #Fullerene Chemistry and Applications #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #cond-mat.mes-hall #thermodynamics and calorimetric analyses
paper · pdf · doi:10.48550/arxiv.1406.5982
16 pages, 5 figures, 1 table
arxiv created 2014/06/23 · openalex publication_date 2014/06/23 · arxiv updated 2014/06/24 · openalex created_date 2016/08/23 · openalex updated_date 2026/07/28
The heat capacity C(T) of the interstitial solid solution (CH4)0.4C60 has been investigated in the temperature interval 1.4-120 K. The contribution of CH4 molecules to the heat capacity has been separated. The contributions of CH4 and CD4 molecules to the heat capacity of the solutions (CH4)0.40C60 and (CD4)0.40C60 have been compared. It is found that above 80K the character of the rotational motion of CH4 and CD4 molecules changes from libration to hindered rotation. In the interval 14-35 K the heat capacities of CH4 and CD4 molecules are satisfactorily described by contributions of the translational and libration vibrations, as well as the tunnel rotation for the equilibrium distribution of the nuclear spin species. The isotope effect in heat capacity of CH4 and CD4 molecules is due, mainly, the difference in the frequencies of local tranlational and libration vibrations of molecules CH4 and CD4. The contribution of the tunnel rotation of the CH4 and CD4 molecules to the heat capacities of this gases is dominant below 8 K. The isotopic effect is caused by the difference between both the conversion rates and the rotational spectra of the nuclear spin species of CH4 and CD4 molecules. The conversion rate of CH4 molecules is several times lower than that of CD4 ones. Weak features observed in the curves of heat capacity of CH4 and CD4 near 6 K and 8 K, respectively, are most likely a manifestation of first-order phase transitions in the orientational glasses of these solutions.