Heat transfer in solidCH4: Influence of an atomic impurity (Kr)

Abstract

The measurements of thermal conductivity of solid methane with krypton impurity ͑concentrations of the impurity were 0.015%, 0.338%, and 1.105%͒ were performed in the temperature range from 1.4 K to 20 K. The analysis of the experimental data of both pure and impurity containing crystals was performed within the framework of the time-relaxation model. The temperature dependence of thermal conductivity of solid methane was described by using the following phonon-scattering processes: boundary scattering, phonon-phonon scattering (U processes͒, scattering by point defects, and elastic interaction with the rotational motion of methane molecules. It was shown that the elastic interaction of phonons with almost freely rotating molecules (O h symmetry sites͒ is the main phonon relaxation process that determines the thermal conductivity of methane in the low-temperature phase. The value of the phonon-rotational interaction parameter in this phase was obtained. The process of resonance phonon scattering on a heavy isotope impurity was used to describe the impurity effect of Kr. The analysis showed that the temperature dependence of thermal conductivity of doped methane can be described with the assumption that the introduction of the atomic impurity of Kr deforms the rotational spectrum of methane.