Crystallographic-orientation-dependent unconventional twinning pathway at the crack tip of body-centered cubic tantalum

Anti-twin has been experimentally observed in body-centered cubic nanopillars, which naturally raises the reconsideration of twinning pathways at the crack tips. Using molecular dynamics simulations, we find that shuffling anti-twinning and twinning pathways appear simultaneously at the (Formula presented.) crack tip; while only twinning pathway appears at the (Formula presented.) crack tip. By analysing the shear stress distribution of the two crack models, we reveal that the specific twinning pathway is determined by the direction relationship between the anti-twinning/twinning slip system and the butterfly-like shear stress fields. This study deepens our understanding of anti-twin and extends the knowledge about the twin formation mechanisms at the crack tips of body-centered cubic metals.