Structure of the (a/2) 〈111〉 Screw Dislocation in α Iron

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Abstract
The atomic positions around the core of the (a/2) 〈111〉 screw dislocation in α iron have been investigated using a new interatomic potential with a cutoff distance between third and fourth neighbors. A radical expansion term has been included in specifying the boundary conditions. Two configurations with about the same core energy were discovered; only one of these retained the threefold symmetry of the lattice around the dislocation line. The energy barrier between the two configurations is about 0.2 eV. The core radius is found to be between one and two Burgers vectors and the core energy between 0.3 and 0.45 eV/atom plane.