Molecular dynamics study of copper nanosprings with/without twin boundary structures

Nanosprings have drawn continuous attention due to their superior elongation and potential applications in stretchable devices. Based on molecular dynamics (MD) simulations, the deformation mechanism of Cu nanosprings with/without twin boundary (TB) structures is investigated in this work. It is found that dislocation-driven deformation mechanism of nanosprings mainly depends on their geometry parameters. During the plastic process, severe distortion caused by local dislocation emission is frequently observed, especially for nanosprings with large wire diameters. Small twin boundary spacings (TBSs) can effectively improve the mechanical properties of nanosprings through restricting dislocation emission and TB migration. In addition, the calculated spring constant reveals that the stiffness of nanosprings with larger wire diameters, smaller helix pitches or smaller TBSs will become larger. It is also worth mentioning that the classical theory is still valid in nanosprings with TB structures. These findings open a new avenue to design novel nanosprings for nanodevices.