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Effect of Hydrogen on The Electronic Structure of a Grain Boundary In Iron

Published online by Cambridge University Press:  26 February 2011

Genrich L. Krasko ,
Ralph J. Harrison  and
G. B. Olson
Genrich L. Krasko
Affiliation:
U. S. Army Materials Technology Laboratory, Watertown, MA 02172–0001
Ralph J. Harrison
Affiliation:
U. S. Army Materials Technology Laboratory, Watertown, MA 02172–0001
G. B. Olson
Affiliation:
Department of Materials Science and Engineering, Northwestern University, Evanston, IL,60208
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Abstract

LMTO-ASA calculations were performed on a 26-atom supercell model of a Σ3(111) grain boundary (GB) in bcc Fe. The supercell emulated two GB's with 11 (111)planes of Fe atoms between the GB planes. One of the GB's was clean, with a structural vacancy at the GB core in the center of a trigonal prism of Fe atoms, while on the other GB this site was occupied by a H atom. The interplanar spacings of the supercell were relaxed using a modified embedded atom method. As in the case of P and S in a similar GB environment in Fe there is only a weak interaction between H and nearest Fe atoms. Almost all the Fe d-states are nonbonding. A very weak covalent bond exists between H and Fe due to s-d hybridization, the hybrid bonding part located far below the Fermi energy. This bond is mostly of σ-type, connecting H with the Fe atoms in the GB plane; the δ-component of this bond across the GB is weaker. A weak electrostatic interaction attracts Fe-atoms across the clean GB, but results in repulsion if a H atom is present. The magnetic contribution to intergranular cohesion is decreased when H is present due the suppression of the magnetic moments of the nearest Fe atoms both in the GB plane and directly across the GB.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 209: Symposium K – Defects in Materials , 1990 , 53
Copyright
Copyright © Materials Research Society 1991

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