Experimental evaluation of the Peierls stresses in a variety of crystals and their relation to the crystal structure

Peierls stresses (τ_P) of dislocations of 66 slip systems in 52 crystals were estimated from experimental data either by direct extrapolation of the critical resolved shear stress (τ_c) vs. temperature curve to absolute zero temperature, or from the T₀ value at which the temperature dependence of τ_c vanishes, based on the kink-pair formation enthalpy, which is a function of τ_P, described by the line tension model of the dislocation. The normalized τ_P/G (G is the shear modulus) values are distributed over four orders of magnitude, but τ_P/G values for a group of crystals with the same crystal structure are within an order of magnitude, indicating a homologous nature of τ_P in crystals. In order to compare the results with the Peierls–Nabarro (P–N) formula generalized to any dislocation character, log(τ_P/G) values were correlated with crystal parameters. In this generalized P–N plot, most of the plots deviate downwards from the Huntington relation (a revised, original P–N relation) and the results of the discretized P–N models of Ohsawa et al. (Ohsawa K, Koizumi H, Kirchner HOK, Suzuki T. Philos Mag A 1994;69:171), with the deviation becoming larger at large h/δ value, where h is the lattice spacing of the glide plane, and δ is the period of the lattice in the direction of the dislocation glide. In the plot, there is a tendency that the stronger the covalent character, the higher the τ_P/G value, reflecting the general tendency of the normalized theoretical shear strength of crystals.