Large scale atomistic simulations of screw dislocation structure, annihilation and cross-slip in FCCNi

Using QM-Sutton-Chen many-body potential, we have studied the 1/2a[1 1 0] s crew dislocation in nickel (Ni) via molecular dynamics (MD) simulations. We have studied core energy and structure using a quadrupolar dislocation sys tem with 3D periodic boundary conditions. The relaxed structures show disso ciation into two partials on {1 1 1} planes. The equilibrium separation dis tance between the two partials is 2.5 nm, which is larger than the derived value according to experimental data, due to low stacking fault energy give n by the QM-Sutton-Chen force field. From our calculations, the core energy for the 1/2a[1 1 0] screw dislocation is 0.5 eV/b. We also studied motion and annihilation process of opposite signed dislocations. We build the dipo le system with two combinations of dissociation planes: (a) two dislocation s dissociated on intersecting slip planes and (b) two on parallel planes. T he process of cross-slip and associated energy barriers are also calculated from these simulations. (C) 2001 Elsevier Science B.V. All rights reserved .