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0220U104239,
0120U105239
,
Quantum tunneling of vibrational excitations in thermal conductivity of crystalline and amorphous materials and composites
Krivchikov Olexander I., Доктор фізико-математичних наук
15-12-2020
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine
During the first stage, the initial results necessary to develop a universal approach to the description of the thermal conductivity of solids were obtained. Within the existing literature theoretical data, it was found that the temperature dependence of both crystalline and amorphous solids is an additive sum of two contributions, where the first is a phonon contribution is associated with oscillatory excitations propagating as quasiparticles, and the second is a diffusion contribution corresponding to quantum tunneling between paired energy states of oscillatory excitations. We have proposed a working formula to describe the temperature dependence of the diffuse contribution. For the first time it was found that this working formula well describes the diffusion contribution as a result of complex theoretical calculations obtained by computer calculation, and the result of experimental temperature dependences of isobaric and isochoric thermal conductivity of molecular amorphous and crystalline materials. The isochoric thermal conductivity of a 1,1-difluoroethane (F-152a freon) molecular crystal for three samples with different molar volumes (Vm = 49.2, 50.25, and 51.5 cm3 / mol) in a dynamically oriented disordered phase was experimentally investigated. It was found to increase with temperature, just as it does in amorphous and vitreous substances above the plateau region in thermal conductivity. It was found that such behavior can be described by a thermoactivation mechanism, with a constant activation energy E, and may depend on the factor k0. The Bridgman coefficient is equal to 6.0 ± 0.5. It was first established that the thermal conductivity of a number of other molecular crystals with a dynamic orientation disorder can be described in a similar way. The obtained results are the first steps in the search for effects due to quantum tunneling of oscillatory excitations in the thermal conductivity of crystalline and amorphous materials and composites.
2020-12-15
Updated: 2025-12-07
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