Thermal conductivity of solid argon

We have formed large-grained essentially free-standing crystals of solid argon. Subsequent in situ measurements of the thermal conductivity $\kappa \mathrm{}\left(T\right)\mathrm{}$ were made by a linear-flow method, covering a temperature range from the triple point, 83.8 K, to liquid-He temperatures. The low-temperature data were highly reproducible within a single run, and of sufficient density to enable quantitative analysis in terms of current theory for heat transport in insulators at low temperatures. In addition, we have performed first-principles calculations of the anharmonic crystal-force contribution to the thermal resistivity, based upon the best-known analytic interatomic-potential models. Results of these calculations indicate that observed deviations from a $T^{-1\mathrm{}}$ high-temperature dependence can be quantitatively explained by the effects of thermal expansion on the lattice vibrational frequencies. At the lowest temperatures, $\kappa$ is seen to be dominated by defect phonon scattering, including a mechanism of of somewhat anomalous behavior.