Orientational isotopic effects in the thermal conductivity of solid CH4/CD4 solutions

Автор(и)

  • A.I. Krivchikov Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
  • P. Stachowiak Institute for Low Temperatures and Structure Research, Polish Academy of Sciences, PN 1410, 50-950 Wroclaw, Poland
  • E. Pisarska Institute for Low Temperatures and Structure Research, Polish Academy of Sciences, PN 1410, 50-950 Wroclaw, Poland
  • A. Jezowski Institute for Low Temperatures and Structure Research, Polish Academy of Sciences, PN 1410, 50-950 Wroclaw, Poland

DOI:

https://doi.org/10.1063/1.2747092

Ключові слова:

thermal conductivity, molecular crystal, orientational disorder, phonon scattering, isotopic effects, phase transition.

Анотація

The thermal conductivity of solid (CH4)1–c(CD4)c solutions with c= 0, 0.03, 0.065, 0.13, 0.22, 0.4, 0.78, and 1.0 has been measured in the region of existence of three orientational phases: disordered (phase I), partially ordered (phase II) and completely ordered (phase III). The temperature range is 1.3–30 K. It is shown that the thermal conductivity has different temperature dependences к(T) in these phases. Its value increases with the degree of the orientational order in the phase. In phase I the thermal conductivity is independent of c and weakly dependent on T. The impurity effect in к(T)is much stronger in the low-temperature part of phase II than in phase III. As the concentration c grows, the к(T) curve of phase II approaches the dependence к(T) typical of phase I. There is a hysteresis in the vicinity of the II↔III phase transition. In phase III the impurity effect in к(T) can be considered as phonon scattering at rotational defects developing due to the difference between the moments of inertia of the CH4 and CD4 molecules. The obtained dependences of thermal conductivity on temperature and concentration can be explained qualitatively assuming that the dominant mechanism of phonon scattering is connected with the interaction of phonons with the rotational motion of the molecules in all of the three orientational phases of the CH4–CD4 system.

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Опубліковано

2007-11-06

Як цитувати

(1)
Krivchikov, A.; Stachowiak, P.; Pisarska, E.; Jezowski, A. Orientational Isotopic Effects in the Thermal Conductivity of Solid CH4/CD4 Solutions. ФНТ 2007, 33, 1393-1400.

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