Large Scale Atomic Simulations of Dislocations in Ni

Yue Qi, Alejandro Strachan, Tahir Cagin and William A. Goddard III

Materials and Process Simulation Center, Caltech, Pasadena, CA 91125

Using QM-Sutton-Chen many-body potential, we have studied the <110>/2 screw dislocation in nickel (Ni) via Molecular Dynamics (MD) simulations. We use a recently developed parallel MD code which allows us to study systems on the order of 105 and 106 of atoms; this program scales well until 128 processors. We have studied different configurations, namely an isolated dislocation in a cylinder with free surfaces, as well as dipole and quadrupole systems with 3-D periodic boundary conditions. The relaxed structures show dissociation into two partials on {111} planes. The equilibrium separation distance between the two partials is 2.1 nm, which agrees well with the experimental value of 2.6+/-0.8nm [Phil. Mag. 35, 1161, (1977)]. We also studied motion and annihilation process of opposite signed dislocations with different combinations of dissociation planes. We analyze the influence of the presence of impurities on kink formation energy and mobility.