Drastic oscillation of peierls stress from peierls-nabarro model calculation and its remedy

Abstract

Peierls stress (τp) of face-centered-cubic (FCC) structures from the Peierls-Nabarro (PN) model calculation is extremely sensitive to the input parameters including the shear modulus (μ), Poisson's ratio (ν) and generalized stacking fault energy (GSFE), which makes the model not a very reliable tool for the prediction of τp because uncertainties occur inevitably in the theoretical calculation or experimental measurements of these input parameters. In the present work, we scrutinized systematically the sensitivity of τps of the FCC metals to the input parameters within the framework of semi-discrete variational PN (SVPN) model. We showed that τp oscillates drastically with varying input parameters. The period of the oscillation is associated with the dependence of the distance between the two partials of the extended dislocation (D) on μ, ν and GSFE while the amplitude of the oscillation is modulated by the dependence of the half-width of the partial dislocation (ζ) on these input parameters. Based on the explored origin of the oscillation, a modified SVPN model is proposed to relieve the sensitivity of τp on the input parameters. The Peierls stresses evaluated with the modified SVPN model are in general agreement with the available experimental values for all the FCC metals.