Atomistic simulations of the graded residual elastic fields in metallic nanowires

The local inhomogeneity of bonding environments in nanomaterials should lead to non-uniform distributions of the surface-induced residual stress and strain (residual elastic fields), which is inconsistent with the conventional assumption of uniform residual quantities. Such graded feature of the residual stress and strain is investigated in this paper based on molecular dynamics (MD) simulations for face-centered-cubic (FCC) metallic nanowires. It is found that the residual stress and strain do not only exhibit sharp variations near boundary surfaces but also have noticeable gradients in the interior of nanowires, and the gradients of residual elastic fields inside nanowires gradually vanish with an increasing characteristic size. Meanwhile, the non-uniformities of residual stress and strain inside [1 0 0] and [1 1 0] axially-oriented nanowires are more significant than those in [1 1 1]-oriented nanowires. Furthermore, by fitting the molecular dynamics (MD) data, sinusoidal and polynomial functions can be obtained to describe the size-dependent graded distributions of residual quantities in square and circular-shaped nanowires. The present work enables ones to better understand the stress and strain states in a relaxed nano-solid, which should be helpful for the mechanical design of nanomaterials.