The orientation dependence of dislocation internal friction in real crystals. I. Alkali halide crystals

In alkali halide crystals, KCl, KBr, NaCl, and LiF, investigations are made of the orientation dependence of the internal friction in the kHz region. It is shown that dislocation internal friction as a function of the angle between the cubic axis and the direction of the distribution of the ultrasound wave is controlled by dislocation mechanism and has a peak in the interval of angles of 20° to 30° in all crystals studied. It is concluded that for interpreting the existence of the maximum on the curve of orientation dependence of internal friction in the crystals with NaCl lattice it is necessary to take into account the possibility of oscillation of some dislocation segments on the cross slip plane and correlation between the slip system {110} 〈110〉 and {100} 〈110〉. [Russian Text Ignored].