Ab initio electronic structure calculations were employed to study the stability and mobility of mono-self interstitial atoms in α-Fe under external deformation. The ab initio results indicated that the volumetric and uniaxial strain dependences of the SIA formation energy were different in the expansion and compression regimes, in contrast to the linear behavior in continuum elasticity theory. A ⟨111⟩→⟨100⟩ SIA reorientation mechanism was found which was induced by uniaxial expansion which proceeded via a ⟨11x⟩∣x=2.7 configuration. Volumetric and uniaxial deformations were also found to have a considerable influence on the migration paths and activation energy barriers for the <110>{110} ↔ <100>{100} transformation and the <111> ↔ <100> reorientation. The results reveal that (i) the volumetric expansion (compression) decreases (increases) substantially the migration energy barrier and renders the diffusion process three (one) dimensional, (ii) the uniaxial strain removes (decreases) the migration energy barrier for the <111> → <11x>∣x=2.7(<11x>∣x=2.7 → <100>) transformation, leading to spontaneous reorientation of the <111> SIA, and (iii) the uniaxial deformation breaks the cubic symmetry of the system and in turn induces anisotropy of the migration rates along different directions. These calculations demonstrate that changes in the electronic structure induced by global elastic deformation lead to additional contributions to the formation and migration energies, which cannot be adequately accounted for neither by elasticity theory nor by empirical interatomic potentials.

Strain-Field Effects on the Formation and Migration Energies of Self Interstitials in α-Fe from First Principles. Z.Chen, N.Kioussis, N.Ghoniem, D.Seif: Physical Review B, 2010, 81[9], 094102