GRAIN BOUNDARY SEGREGATION OF HYDROGEN IN BCC IRON: ELECTRONIC STRUCTURE

S. B. Gesari, M. E. Pronsato and A. Juan ()
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S. B. Gesari: Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, 8000 Baha Blanca, Argentina
M. E. Pronsato: Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, 8000 Baha Blanca, Argentina
A. Juan: Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, 8000 Baha Blanca, Argentina

Surface Review and Letters (SRL), 2002, vol. 09, issue 03n04, 1437-1442

Abstract: The electronic properties of H impurity in an Fe Σ = 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 Σ = 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 significant weakening of the interatomic bonding. H–H interaction was also analyzed.

Keywords: Grain boundary; bcc iron; hydrogen embrittlement; DOS; COOP (search for similar items in EconPapers)
Date: 2002
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DOI: 10.1142/S0218625X02003998

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