Molecular dynamics simulation of loading rate and surface effects on the elastic bending behavior of metal nanorod

The bending behavior of copper nanorod is studied by three-dimensional molecular dynamics simulation. The embedded-atom-method (EAM) potential presented by Johnson was employed to represent the atomic interactions. Gear algorithm used to integrate Newtonʹs equations of motion uses up to the fifth time derivative of the atom positions. The loading–deflection curves are obtained for different loading rates. It is found that the curves are not linear for impact loading rates because of time scale effect. For quasi-static loading, the atomistic simulation result of deflection is different from that predicted through continuum mechanics by using effective elastic modulus of copper nanorod. We owe this difference to the surface effect. Self-balanced stresses exist in the cross-section of the nanorod at the free relaxation state; inner is compression and near surface is extension. The ratio of surface-to-volume is remarkable for materials with nanoscale, and the materials cannot be considered as homogeneous. These nano features must be accounted into the continuum model to correctly predict the mechanical properties of structures and materials at nanoscale.