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

Abstract

The isochoric thermal conductivities of solid (CO₂)₀,₉₀₅Kr₀,₀₉₅ and (CO2)₁₋xXex(x = 0.052 and 0.097) solution of different densities was 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 solid CO₂/Kr and CO₂/Xe 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 gains more freedom as the spherically symmetrical inert gas atoms dissolve in CO₂.