A comparative study of the electronic structure of H pairs near a/2 and a[0 1 0] dislocations in bcc Fe

The H–Fe interaction in a dislocated bcc structure was studied using qualitative electronic structure calculations in the framework of the atom superposition and electron delocalisation molecular orbital (ASED-MO) theory. The effect on the electronic structure after introducing an a /2 [1 1 1] mixed dislocation was analyzed and compared with the effect of introducing an a [0 1 0] edge dislocation. Calculations were performed using Fe 85 clusters to simulate a dislocated bcc structure. The cluster geometry and atomic parameters were optimized to make a better approximation to the repulsive energy terms. The most stable positions for two H atoms inside the cluster were determined. The total energy of the cluster decreases when the H atoms are located near the dislocation void, making it a possible region for H-accumulation. The hydrogen atoms bond to their closest neighbors weakening 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 neighbors result to have similarities for both dislocations analyzed.