Extraordinary temperature dependence of isochoric thermal conductivity of crystalline CO2 doped with inert gases.

The isochoric thermal conductivities of the solid solutions (CO2)0.905Kr0.095 and (CO2)1-xXex (x=0.052 and 0.097) of different densities are investigated in the temperature interval from 150 K to the onset of melting. An unusual effect of point defects on the thermal conductivity has been detected. In pure CO2 at T>150 K the isochoric thermal conductivity decreases smoothly with increasing temperature. In contrast, the thermal conductivity of CO2/Kr and CO2/Xe solid solutions first decreases, passing through a minimum at 200–210 K, and then starts to increase with temperature up to the onset of melting. This behavior of the isochoric thermal conductivity is attributed to the rotation of the CO2 molecules, which gain more freedom as the spherically symmetrical inert gas atoms are dissolved in the CO2. [ABSTRACT FROM AUTHOR]