Low Temperature Physics: 29, 422 (2003); https://doi.org/10.1063/1.1542506 (7 pages)
Fizika Nizkikh Temperatur: Volume 29, Number 5 (May 2003), p. 567-576    ( to contents , go back )

Heat transfer by low-frequency phonons and "diffusive" modes in molecular crystals

V.A. Konstantinov

B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Science of Ukraine, 47 Lenin Ave., Kharkov, 61103, Ukraine
E-mail: konstantinov@ilt.kharkov.ua
pos Анотація:

Received October 2, 2002

Abstract

A model is suggested to describe the behavior of thermal conductivity of molecular crystals in the orientationally ordered phases, which assumes that the heat is transferred by low-frequency phonons and above the mobility edge by "diffusive" modes. The mobility edge w0 is determined from the condition, according to which the phonon mean-free path restricted by the Umklapp processes, cannot be smaller than half the phonon wavelength. The Bridgman coefficientg g= - (∂lnL/∂lnV)T is weighted average over these modes whose volume dependences are very different. Using the model suggested, the thermal conductivity of CO2, N2O, naphthalene C10H8, anthracene C14H10, and hexamethylenetetramine (CH2)6N4 is discussed. It is shown that when calculating of the lower limit to thermal conductivity of molecular crystals the rotational energy transfer from the site to site should be taken into account.

PACS:
66.70.+f - Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves (for thermal conduction in metals and alloys, see 72.15.Cz and 72.15.Eb)
63.20.Ls - Phonon interactions with other quasiparticles

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