Thermal conductivity of solid parahydrogen with methane admixtures

The thermal conductivity of a solid parahydrogen crystal with methane admixtures was measured in the temperature range 1.5 to 8 K. Solid samples were grown from the gas mixtures at 13 K. The concentration of CH4 admixture molecules in the gas varied from 5 to 570 ppm. A very broad thermal conductivity peak with an absolute value of about 110 W/(m.K) was observed at 2.6 K. The data were interpreted using Callaway's model with resonance scattering of phonons by quasilocal vibrations of CH4 molecules and phonon-grain boundary and phonon-phonon scattering. As grain boundary scattering increases, the broadening of the peak decreases. The analysis shows that a solid mixture of p-H-2 and CH4 is a heterogeneous solution for CH4 concentration higher than 0.1 ppm. (C) 2003 American Institute of Physics.