The formation of stacking fault tetrahedra in Al and Cu: III. Growth by expanding ledges

Ledge expansion and the concomitant growth of a stacking fault tetrahedron (SFT) are investigated in Al and Cu by molecular dynamics (MD) simulations by addition of vacancy rods with selected lengths. Ledge expansion is largely governed by the site preference of vacancies on the SFT edges resulting in distinct stable ledged SFTs. Both edge- and corner-facing ledge configurations may be adopted. The growth of SFTs, especially large ones, is controlled by thermal agitation. The mobile part of the ledges consists of a dipole of Shockley partials generally oriented in the 60° mixed orientation that move in a thermally activated manner, reflecting a certain core reorganization of the Shockley dipole.