The theory for description of the stress peak (yield drop) on the stress–strain curves of covalent crystals with low and zero dislocation densities has been developed. The kinetics of the variation of the dislocation density and the shape of the stress peak in the vicinity of the upper yield stress is described analytically within the framework of the generalized Alexander–Haasen model. The character of the elastoplastic transition is analyzed in detail and the model is compared with the experimental data for silicon.
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