Grain boundary segregation of hydrogen in bcc iron: electronic structure

S. B. GESARI; M. E. PRONSATO; A

SURFACE REVIEW AND LETTERS

World Scientific Publishing Company

Año: 2002 vol. 9 p. 1437 - 1442

0218-625X

The electronic properties of H impurity in an Fe _ = 5, 53:1_ [100] (012) symmetrical tilt grain boundary (GB) were studied using qualitative electronic structure calculations in the framework of the atom superposition and electron delocalization molecular orbital (ASED-MO) theory. A large cluster containing 197 Fe atoms was used to simulate the local environment of the boundary. The most stable positions for one H atom and two H atoms at the GB core were determined. The total energy of the cluster decreases when the H atoms are at that location, making it a possible site for H accumulation. The binding energy found was less than that of a _ = 5 [100] (013) GB. An analysis of the orbital interaction reveals that H{Fe bonding involves mainly the Fe 4s and H 1s orbitals. A higher contribution of d orbitals is present, which show a different behavior when compared with mixed dislocation and vacancy in the bulk Fe. The interatomic bonding along the Fe atom chains via H atoms is very inefficient, thus resulting in signifficant weakening of the interatomic bonding. H{H interaction was also analyzed.