Classical molecular dynamics simulations of the deformation of metals under uniaxial monotonic loading: A review

Nanoscale features present in structural and functional materials affect their macroscopic properties and hence have been extensively studied. As experimental investigations of different nanoscale events can be tedious, computational techniques evolved as a cost-cutting method to replace or complement difficult to perform experiments. Classical molecular dynamics (MD) simulation is an effective tool to study the effect of specific nanostructural features on the overall mechanical behavior of the material. This article reviews the MD simulation of the mechanical behavior of metal crystals under uniaxial monotonic loading with and without the presence of defects such as grain boundaries (GBs), voids, and cracks. MD simulations showed that along with shear stress obtained through the Schmid factor, the normal stress to the slip plane also influenced the slip of the single crystals, and that the stacking fault energy (SFE) controlled dislocation and twin nucleation. GBs were observed to be regions of dislocation nucleation. Along with the grain size effect, the SFE also affected the deformation mechanism, such as changing it from dislocation slip in the grain to GB slip. MD simulations showed that voids and cracks emit dislocations and that the type of dislocations emitted depended on the SFE of the material. The nucleation of trailing partial dislocations on an adjacent plane to the leading partials resulted in twin formation. For configurations containing both GB and cracks, MD simulations showed that twist GBs were more resistant to crack propagation as compared to tilt GBs. The critical stress required for dislocation nucleation from the GB was dependent on its GB energy and structure. In presence of low angle GBs and Σ GBs, voids became energetically favorable sites for dislocation nucleation. Low angle GBs and Σ GBs require higher critical stress for dislocation nucleation as compared to voids.