The electronic effect of carbon and hydrogen in an (1(1)over-bar1) edge dislocation core system in bcc iron

The Fe-C-H interaction in a dislocated bee structure was studied using qualitative structure calculations in the framework of the atom superposition and electron delocalisation molecular orbital (ASED-MO) theory. Calculations were performed using Fe-85 cluster to simulate a dislocated bee structure. The cluster geometry and atomic parameters were optimised to make a better approximation to the repulsive energy terms. The most stable position for C atom inside the cluster was determined. Therefore, and H atom was approximated to the minimum energy region where the C atom was previously located. The total energy of the cluster decreases with the C atom near the dislocation core. The a/2[111] dislocation creates an energetically favourable zone for accumulation of C. The presence of C in the dislocation core make no favourable H accumulation. The C acts such as an expeller of H and could reduce the weakening of Fe-Fe bonds. In addition, a sort of Fe-C-Fe "bridge" could prevent dislocation displacement if a shear stress would be applied. (C) 2003 Elsevier Science B.V. All rights reserved.