First-principles methods are employed to investigate the structure relaxati
on and the electronic structure of a N impurity in an (100) edge dislocatio
n core (DC) system in alpha -iron. A 96-atom cluster model is used to simul
ate the local environment of N impurity in the edge dislocation. By use of
the DMol method, we obtained an optimized atomic configuration for the syst
em by calculating the forces on N impurity and its neighboring Fe atoms, an
d by minimizing the total energy of the cluster model. The optimization res
ults show that the N impurity moves away from compression region to a stabl
e position in the dilated region. By use of the discrete variational (DV) m
ethod, we calculated energetic parameters (structural energy and interatomi
c energy) and charge distribution. From these results, one can find that N
impurity has a strong interaction with its adjacent Fe atoms in the DC syst
em. Moreover, notable charge redistribution between the N impurity and Fe a
toms indicates the formation of N impurity-Fe dislocation complex, which im
plies the trapping effect of DC on N impurity. (C) 2001 Elsevier Science B.
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