Simulation of mechanical response and internal friction by point defects

Structures and dynamical behaviors of atoms in crystals containing self-interstitials have been investigated by means of molecular dynamics simulations. Embedded atom method potential for copper was used in the simulation. Model crystals consist of 11,000 atoms and include several self-interstitials. Motions of interstitials at elevated temperatures are investigated by monitoring the trajectory of atoms. Simultaneous jumps of several atoms near the interstitial are observed. Motion of interstitial atoms under an elastic vibration of model crystals is also investigated. The internal friction is estimated from the decay of free oscillation of model crystals. The internal friction increases by the introduction of interstitials and the internal friction for one interstitial is estimated to be the order of 10-4 at the frequency of 230 GHz.