Phonon-libron interaction and thermal conductivity in the simplest molecular crystals

The thermal conductivity of solid N2, CO, N2O, and CO2 is studied experimentally and theoretically. Experimental studies were performed over the following temperature ranges: N2, 23–55°; CO, 23–58°; N2O, 24–120°; and CO2, 27–123°K. The effect of small angular oscillations of the molecules (librations) on the heat transfer process is considered. It is shown that the basic mechanism determining thermal resistance in these crystals in the high temperature range (T>ΘD/4) is phonon scattering by the libron subsystem. A collision integral is constructed for the description of the phonon-libron interaction processes with consideration of one-and two-libron-phonon scattering processes. Good agreement was obtained between calculated and experimental values of the coefficient of thermal conductivity.

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