First-principles methods were used to investigate structural relaxation and the electronic structure of a N impurity in an <100> edge dislocation core system in α-Fe. A 96-atom cluster model was used to simulate the local environment of the N impurity in the edge dislocation. By using molecular dynamics methods, an optimized atomic configuration was obtained for the system by calculating the forces on the N impurity and the neighboring Fe atoms, and by minimizing the total energy of the cluster model. The optimization results showed that the N impurity moved away from the compressive region, to a stable position in the dilated region. By using the discrete variational method, energetic parameters (structural energy, interatomic energy) and charge distributions were calculated. From these results, it was deduced that the N impurity underwent strong interaction with the adjacent Fe atoms in the dislocation core system. A notable charge redistribution between the N impurity and the Fe atoms indicated the formation of a N-impurity plus Fe-dislocation complex; which implied the existence of a trapping effect of the dislocation core upon the N impurity.

The Electronic Effect of N Impurity in an <100> Edge Dislocation Core System in α-Iron. Y.Niua, S.Y.Wang, D.L.Zhao, C.Y.Wang: Computational Materials Science, 2001, 22[3-4], 144-50