Low-temperature thermal conductivity of cryocrystals formed by linear three-atom molecules

Abstract

Thermal conductivity of ${\mathrm{CO}}_{2}$ and ${\mathrm{N}}_{2}\mathrm{O}$ solids has been investigated over the temperature range $1--40\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The thermal conductivity coefficient of ${\mathrm{CO}}_{2}$ and ${\mathrm{N}}_{2}\mathrm{O}$ exhibits, in the whole investigated temperature range, surprisingly high value when compared with other ${\mathrm{N}}_{2}$-type molecular crystals. Analysis of the experimental data, in framework of the Debye model, indicates that relatively big size of the crystal grains, low density of dislocations and weak phonon--phonon interaction might be reasons for the good thermal conduction in these crystals at temperatures near the maximum of the thermal conductivity. It has been found that there is an additional (in comparison with ${\mathrm{CO}}_{2}$) significant mechanism of scattering of phonons in ${\mathrm{N}}_{2}\mathrm{O}$. Supposedly this scattering occurs on the end-to-end disordered ${\mathrm{N}}_{2}\mathrm{O}$ molecules.