Low-Temperature Deformation and Dislocation Mechanism in LiF

Abstract

The temperature and strain-rate dependence of the critical resolved shear stress of LiF single crystals has been measured in the temperature range from 4.5 to 300K. The results are analysed on the basis of the thermally activated deformation process. The data below 20K are shown to correlate well with the requirements of the Peierls mechanism. The Peierls stress is deduced to be 2.0 kg/mm² when the parabolic Peierls potential is assumed, and 1.7₅ kg/mm² for the sinusoidal case. The estimated value of the activation energy is about 0.09 eV, which give a reasonable value for the line energy of a dislocation. The activation volumes determined by changes in strain rate also exhibit the proper trends for the Peierls mechanism.