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A mechanism is proposed of the rapid annihilation of mixed dislocations by means of the cross‐slip of the double kink on the screw segment of the dislocation. The maximum annihilation distance R between dislocations as a function of applied stress σ, dislocation friction stress σ0, and angle α between the dislocation line and the Burgers vector b is correctly calculated. The comparison is made of theoretical results with available experimental data and previous rough theoretical estimations. It is shown that the annihilation mechanism is weakly connected with thermal fluctuations and it mainly has a pure force nature.

A universal mechanism for initial defect nucleation in metals and transparent dielectrics, as the sample is irradiated by 'pre-threshold' laser pulses, is proposed. The theoretical model uses the newly described effect of local accumulation of elastic energy due to anharmonic parametric resonance between vibrations localised in an inhomogeneity of the crystal lattice and laser-produced acoustic waves in the solid. Thermal density fluctuation is considered as a universal inhomogeneity of solid matter. The elastic modulus plays the role of an excited parameter, and the coupling constant between this parameter and the elastic wave is the Gruneisen coefficient. Metals and transparent dielectrics have different mechanisms of acoustic wave generation due to laser beam interaction with matter. The thermoelastic effect arising due to pulsed heating of the irradiated region is a source of acoustic waves in metals. Hyperacoustic waves are generated due to stimulated Brillouin scattering in the case of transparent dielectrics. The model explains the main characteristics of laser-induced damage in solids subjected to 'pre-threshold' irradiation. Quantitative estimates have shown that the critical values of the acoustic wave amplitude, under which the proposed mechanism is effective. are within the error bars of the experimental values for both transparent dielectrics (cu-Al,O,crystals, amorphous S O z ) and a typical metal (AI). Several theoretical predictions are compared with original, previously published, results.

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