Low Temperature Anomaly of Heat Capacity of CD4 Rotors in Solid CD4–Kr Solution

Bagatskii, M. I.; Dudkin, V. I.; Manzheliı̆, V. G.; Mashchenko, D. A.; Feodosyev, S. B.

doi:10.1007/s10909-005-5442-6

Cited by 4 publications

(7 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The conversion of molecules deuteromethane has been first found in the solid solutions (CD 4 ) x Kr. 35,36 The behavior of the experimental temperature dependences s CH4 (T) and s CD4 (T), 13 as in cases of solid solutions (CH 4 ) x Kr, 32,33 (CD 4 ) x Kr, 35,36 agrees qualitatively with the theoretical data on conversion in multiatomic molecules. In contrast to diatomic molecules, [37][38][39][40] other mechanisms of conversion are dominant in multiatomic molecules at low temperatures.…”

Section: Resultssupporting

confidence: 69%

Low-temperature dynamics of matrix isolated methane molecules in fullerite C60: The heat capacity, isotope effects

Bagatskii

Manzheliı̆

Sumarokov

et al. 2014

Low Temperature Physics

Self Cite

View full text Add to dashboard Cite

The heat capacity of the interstitial solid solution (CH 4 ) 0.4 C 60 has been investigated in the temperature interval 1.4-120 K. The contribution of CH 4 molecules to the heat capacity of the solution has been separated. The contributions of CH 4 and CD 4 molecules to the heat capacity of the solutions (CH 4 ) 0.40 C 60 and (CD 4 ) 0.40 C 60 have been compared. It is found that above 90 K the character of the rotational motion of CH 4 and CD 4 molecules changes from libration to hindered rotation. In the interval 14-35 K the heat capacities of CH 4 and CD 4 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 is due to mainly, the difference in the frequencies of local translational and libration vibrations of molecules CH 4 and CD 4 . The contribution of the tunnel rotation of the CH 4 and CD 4 molecules to the heat capacity 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 CH 4 and CD 4 molecules. The conversion rate of CH 4 molecules is several times lower than that of CD 4 ones. Weak features observed in the curves of temperature dependencies of the heat capacity of CH 4 and CD 4 molecules near 6 and 8 K, respectively, are most likely a manifestation of first-order polyamorphic phase transitions in the orientational glasses of these solutions. V C 2014 AIP Publishing LLC. [http://dx

show abstract

Section: Resultssupporting

confidence: 69%

Low-temperature dynamics of matrix isolated methane molecules in fullerite C60: The heat capacity, isotope effects

Bagatskii

Manzheliı̆

Sumarokov

et al. 2014

Low Temperature Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…The time constant τ for the relaxation of the CD 4 molecules to the equilibrium distribution of the nuclear spin species is described as [52]: The characteristic conversion time τ ≈ 0.1 h of the CD 4 molecules in the (CD 4 ) 0.40 (C 60 ) solution at 4 K is about 25 times shorter than the conversion time t 1/2 ≈ 2.6 h (obtained from inelastic neutron scattering data [13]) of the CH 4 molecule in the (CH 4 ) 0.92 (C 60 ) solution. The discrepancy suggests that at low temperatures a hybrid mechanism [57] of molecule conversion is dominant in the systems investigated, as in solid solutions of (CH 4 ) x Kr [52,54] and (CD 4 ) x Kr [55,56]. In Kr solutions with 5% of CD 4 and CH 4 the average conversion rate of CD 4 molecules at liquid helium temperatures is six times higher than that of the CH 4 molecules.…”

mentioning

confidence: 92%

Low-temperature heat capacity of fullerite C60 doped with deuteromethane

Bagatskii

Sumarokov

Долбин

et al. 2012

Low Temperature Physics

Self Cite

View full text Add to dashboard Cite

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 ...

show abstract

“…However, the rotational motion becomes rather intricate in solution with n > 0.05CD 4 , where the noncentral interaction is essentially important [10]. The temperature dependences of the heat capacity of the rotational subsystem C rot (T ) in concentrated (CD 4 ) n Kr 1−n solutions [2] are drastically different from C rot (T ) in (CD 4 ) n Kr 1−n solutions with n = 0.01, 0.05 CD 4 [7,8] and (CH 4 ) n Kr 1−n solutions with n = 0.1-0.78 CH 4 [1,2,11].…”

Section: Introductionmentioning

confidence: 92%

“…In contrast, in the case of strong molecular interaction (N 2 , CO in Kr), even one molecule present in the first coordination sphere can cause qualitative changes in the molecule rotation and the rotational spectrum [4][5][6]. In the (CD 4 ) n Kr 1−n system with CD 4 concentrations n 0.05 the rotation of most of the molecules, as in CH 4 -Kr solution, is weakly hindered and their rotational spectrum is close to that of matrix-isolated molecules [7][8][9]11]. However, the rotational motion becomes rather intricate in solution with n > 0.05CD 4 , where the noncentral interaction is essentially important [10].…”

Section: Introductionmentioning

confidence: 99%

Effect of octupole interaction on the rotational motion of rotors in a solid Kr–CD₄solution

Dudkin¹,

Bagatskii²,

Mashchenko³

2007

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

The heat capacity of solid (CD4)nKr1−n solutions with CD4 concentrations n = 0.09, 0.17, 0.25, 0.35 and solutions with n = 0.25 doped with 0.0005, 0.0021 and 0.0123 of O2 impurity has been investigated at T = 0.6–30 K. It is found that the molecular field responsible for a qualitative change in the rotational motion of the rotators increases sharply as the number of nearest neighbours increases from one to three. Below 1.6 K the temperature dependence of the heat capacities of the rotational subsystems of the solutions can be described by a sum of the contributions made by molecules finding themselves in effective weak, moderate and strong molecular fields. The average concentration and the effective energy differences between the ground and the first excited energy levels of the CD4 molecules in the above mentioned fields have been estimated. It is shown that the considerable changes in the experimental heat capacities of the rotational subsystem normalized to a mole of rotors are mostly due to the changes in the relative concentrations x(n) of the rotors in these molecular fields. Above T = 0.6 K the nuclear-spin A, T and E species of the molecules reach equilibrium distribution within one measurement of the heat capacity. The O2 impurity is found to produce great influence on the heat capacity of the rotational subsystem in the solution with n = 0.25 and the equilibrium composition of the nuclear-spin species of the molecules.

show abstract

Low Temperature Anomaly of Heat Capacity of CD4 Rotors in Solid CD4–Kr Solution

Cited by 4 publications

References 8 publications

Low-temperature dynamics of matrix isolated methane molecules in fullerite C60: The heat capacity, isotope effects

Low-temperature dynamics of matrix isolated methane molecules in fullerite C60: The heat capacity, isotope effects

Low-temperature heat capacity of fullerite C60 doped with deuteromethane

Effect of octupole interaction on the rotational motion of rotors in a solid Kr–CD₄solution

Contact Info

Product

Resources

About

Low Temperature Anomaly of Heat Capacity of CD4 Rotors in Solid CD4–Kr Solution

Cited by 4 publications

References 8 publications

Low-temperature dynamics of matrix isolated methane molecules in fullerite C60: The heat capacity, isotope effects

Low-temperature dynamics of matrix isolated methane molecules in fullerite C60: The heat capacity, isotope effects

Low-temperature heat capacity of fullerite C60 doped with deuteromethane

Effect of octupole interaction on the rotational motion of rotors in a solid Kr–CD4solution

Contact Info

Product

Resources

About

Effect of octupole interaction on the rotational motion of rotors in a solid Kr–CD₄solution