Atomistic modeling of helium interacting with screw dislocations in α-Fe

Formation energies, binding energies, and migration energies of interstitial He atoms in and near the core of an a/2〈1 1 1〉 screw dislocation in α-Fe are determined in atomistic simulations using molecular statics employing conjugate gradient relaxation and the dimer method for determining saddle point energies. The set of interatomic potentials employed is the same as used in many recent static and dynamic He–Fe simulations. Interstitial He atoms have a maximum positive binding energy of about 1 eV to the screw dislocation core relative to interstitial He atoms in the perfect crystal, which is about half that of binding energies of He to the edge dislocation. However, interstitial He atoms diffuse along the screw dislocation core with a migration energy of 0.4–0.5 eV, which is the same range as migration energies of interstitial He atoms along the edge dislocation.