Electronic structure and bonding of hydrogen in a screw dislocated bcc Fe

The bonding of H±Fe is analyzed using qualitative electronic calculations in the framework of the atom superposition and electron delocalization orbital cluster method (ASED-MO). The changes in the electronic structure of bcc Fe upon introduction, a screw dislocation are compared with Fe surfaces. A comparison is drawn with H adsorption at Fe …1 12† surface and H absorption in the bulk Fe with a dislocation. The results suggest that the detrimental effect of H on the Fe±Fe bonds in a screw dislocation is almost half-severe than in other defects, such as an edge dislocation or vacancy and it is limited to its ®rst neighbor. An analysis of the orbital interaction reveals that Fe±H bonding involves mainly the Fe 4s and H 1s orbitals. When H is in the bulk, the region near screw dislocation core is much more repulsive than in a normal Fe lattice. These results allow us consider that H accumulation could be less favorable near a screw dislocation than an edge dislocation. # 2001 Elsevier Science B.V. All rights reserved.