THERMAL-CONDUCTIVITY OF THE IH AND XI PHASES OF ICE

The thermal conductivity lambda of KOH-doped ice was measured using the transient hot-wire method at temperatures in the range 55-250 K and at pressures up to 0.15 GPa. With an isobaric increase of temperature at 0.08 GPa, lambda decreased 17% at about 74 K. This decrease is associated with the known transition from ordered phase XI to phase Ih which exhibits orientational disorder of H2O. A model for lambda indicates that the decrease of lambda at the transition is due to an increase of the lattice anharmonicity which might be caused by the disorder in phase Ih. It was inferred from the temperature dependence of lambda that phonon scattering in both phases Ih and XI is dominated by three phonon unklapp processes. At 58 K, lambda of supercooled phase Ih decreased slightly with increasing pressure whereas lambda of phase XI was independent of pressure.