Molecular Dynamic (MD) calculations are suitable to describe the discrete nature of nanoscale materials. Classical MD usually solves atomic motions governed by the Newton’s second law, where the interaction between atoms or particles is described by empirical potentials. The accuracy and efficiency of MD calculations are strongly dependent on the empirical potentials employed. As an example of MD simulations, the defect evolution and propagation in metal nano films are examined.

Mainly observed defects in metal film under the external loading are dislocations (line defect). The dislocations in metal are usually lied on a slip plane (111), and are split into stacking fault surrounded by two partial dislocations. Tow dislocation indicated by 1 & 2 in (a) make a jog dislocation in (b). When a jog dislocation moves there leaves a chain of vacancy as a trail. MD is a powerful tools to observe the complicate interaction of moving atoms.