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Thermal conductivity Λ P of solid cyclohexane is measured at a pressure P = 0.1 MPa in the temperature range from 80 K to the melting point, which covers the ranges of low-temperature orientationally ordered phase II and high-temperature orientationally disordered phase I. Thermal conductivity Λ V is measured at a constant volume in orientationally disordered phase I. The thermal conductivity measured at atmospheric pressure decreases with increasing temperature as Λ P ∝ T −1.15 in phase II, whereas Λ P ∝ T −0.3 in phase I. As temperature increases, isochoric thermal conductivity Λ V in phase I increases gradually. The experimental data are described in terms of a modified Debye model of thermal conductivity with allowance for heat transfer by both phonons and “diffuse” modes.

The isochoric thermal conductivity of Kr1−ξXeξ solid solutions (ξ=0.034, 0.072, and 0.14) is investigated in the temperature range from 80 K to Tm (Tm is the melting temperature) for samples of different densities. It is found that an increase in disordering of the crystal leads to a gradual crossover from the thermal conductivity of a perfect crystal to the lower limit of the thermal conductivity of the lattice. A quantitative description of the results obtained is performed within the Debye model of thermal conductivity and allows for the fact that the mean free path of phonons cannot be less than half the phonon wavelength.