Thermal conductivity of molecular crystals of monoatomic alcohols: from methanol to butanol

Анотація

Experimental data on the thermal conductivity κ(T) of some simple alcohols have been compared, analyzed and generalized. The objects of investigation were methyl, protonated and deuterated ethyl, 1-propyl and 1-butyl alcohols in the thermodynamically equilibrium phase with a complete orientational order. The temperature interval was from 2 K to the melting point under the equilibrium vapor pressure. It is found that in the region above the temperature of the maximum thermal conductivity κ(T) deviates from the 1/Т law. This is because the total thermal conductivity has an extra contribution κ_II(T) of short-lived phonons in addition to κ_I(T) contributed by propagating phonons: κ(T) = κ_I(T) + κ_II(T). The contribution κ_I(T) is well described by the Debye–Peierls model allowing for the phonon–phonon processes and scattering of phonons by dislocations. At Т > 40 K the contribution κ_I(T) obeys the law A/Т and κ_II(T) is practically temperature-independent. It is shown that the Debye temperature Θ_D of alcohol is dependent on the molecular mass as Θ_D = 678М ^–0.42 K and the coefficient А characterizing the intensity of the phonon–phonon scattering increases with the molecular mass of the simple monoatomic alcohol by the law А = 0.85М ^0.8 W/m, which suggests a decreasing intensity of the phonon–phonon process.