Low-temperature specific heat of deformed lithium fluoride crystals

The specific heat and thermal conductivity of heavily deformed crystals of LiF were measured over the temperature range 0.08-4 K. To within the resolution of the experiment (∼ 1%), the specific heat did not change with deformation, contrary to a previous report. A density of localized excitations associated with dislocation dipoles was deduced from the thermal-conductivity measurements. The lack of an observable contribution to the specific heat is consistent with theoretical predictions based upon a density of dislocation dipoles of ∼${10}^9$ ${\mathrm{cm}}^{-2\mathrm{}}$.