Publication Date:
2016-01-30
Description:
The thermal conductivity of solid thiophene at equilibrium vapor pressure between 2 K 〈 T 〈 170 K, has been measured in a sequence of incommensurate metastable orientationally disordered phases II, II 1 , II 2 , and II 2 g with different degrees of orientational ordering of the molecules. It is found that in phase states II, II 1 and II 2 with dynamic orientational disorder of the molecules, the thermal conductivity does not depend on the temperature. It is shown that the temperature dependence of the thermal conductivity κ( T ) of orientational glass V g and II 2 g (incommensurate) does not have any of the anomalies that are typical for amorphous materials and glasses. The temperature dependence κ( T ) of the incommensurate state of orientational glass II 2 g is bell-shaped, which is typical for the thermal conductivity of crystals with long-range orientational order. In the II 2 g state, as temperature drops from T g to almost 10 K, the thermal conductivity increases according to κ( T ) = A / T + B , where the first term describes the input of the propagating phonons, wherein the average length of their mean free path is greater than half of the phonon wavelength. The B term is associated with the input of localized short-wave, or “diffuse” vibrational modes. At low temperatures T ≤ 7 K, κ( T ) ∝ T 3 is observed with increasing temperatures, which corresponds to the boundary scattering of phonons.
Print ISSN:
1063-777X
Electronic ISSN:
1090-6517
Topics:
Physics
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