A comparative study of the electronic structure of H pairs near a/2[1 (1)over-bar1] and a[010] dislocations in bcc Fe

The H-Fe interaction in a dislocated bcc structure was studied using qualit ative electronic structure calculations in the framework of the atom superp osition and electron delocalisation molecular orbital (ASED-MO) theory. The effect on the electronic structure after introducing an a/2 [1 (1) over ba r 1] mixed dislocation was analyzed and compared with the effect of introdu cing an a[0 1 0] edge dislocation. Calculations were performed using Fe-85 clusters to simulate a dislocated bcc structure. The cluster geometry and a tomic parameters were optimized to make a better approximation to the repul sive energy terms. The most stable positions for two H atoms inside the clu ster were determined. The total energy of the cluster decreases when the H atoms are located near the dislocation void, making it a possible region fo r H-accumulation. The hydrogen atoms bond to their closest neighbors weaken ing the bond between iron atoms. The H-H interaction was also analyzed. In general, the behavior of H and its influence on the Fe atoms first neighbor s result to have similarities for both dislocations analyzed. (C) 2001 Else vier Science B.V. All rights reserved.