Dynamic Behaviour of Dislocations in HF-Doped Ice Ih

Abstract

AbstractA model of dislocation glide in ice Ih was recently proposed. This model was developed on certain assumptions, namely that transitions occur through cooperative movements of H2O molecules in the non-crystalline core of dislocations. A relation between the velocityvdof linear defects and shear stressτor temperatureTis obtained. This relation shows thatvdvaries linearly withτat low values ofτand (or)Tbut varies more rapidly at higher stresses; this non-linearity is more pronounced the higher the temperature. Such an analysis is extended in order to take into account doping effects. The case of HF-doped ice is considered: it is shown that there is a strong accumulation effect of HF molecules in the dislocation cores, which induces an increase of the rate of transitions. The results are in agreement with experimental data concerning both the velocity of dislocations and high-temperature internal friction in HF-doped ice.