Temperature-dependent ideal strength and stacking fault energy of fcc Ni: a first-principles study of shear deformation

Abstract

Variations of energy, stress, and magnetic moment of fcc Ni as a response to shear deformation and the associated ideal shear strength (τIS), intrinsic (γSF) and unstable (γUS) stacking fault energies have been studied in terms of first-principles calculations under both the alias and affine shear regimes within the {111} slip plane along the and directions. It is found that (i) the intrinsic stacking fault energy γSF is nearly independent of the shear deformation regimes used, albeit a slightly smaller value is predicted by pure shear (with relaxation) compared to the one from simple shear (without relaxation); (ii) the minimum ideal shear strength τIS is obtained by pure alias shear of ; and (iii) the dissociation of the dislocation into two partial Shockley dislocations () is observed under pure alias shear of . Based on the quasiharmonic approach from first-principles phonon calculations, the predicted γSF has been extended to finite temperatures. In particular, using a proposed quasistatic approach on the basis of the predicted volume versus temperature relation, the temperature dependence of τIS is also obtained. Both the γSF and the τIS of fcc Ni decrease with increasing temperature. The computed ideal shear strengths as well as the intrinsic and unstable stacking fault energies are in favorable accord with experiments and other predictions in the literature.