TY - JOUR
T1 - Electronic bonding characteristics of hydrogen in bcc iron
T2 - Part II. Grain boundaries
AU - Itsumi, Yoshio
AU - Ellis, D. E.
N1 - Funding Information:
This work was supported by Kobe Steel, Ltd., the Office of Naval Research, Grant No. N00014-90-J-1363, and by the MRL Program of the National Science Foundation, at the Materials Research Center of Northwestern University, under Award No. DMR-9120521. We thank G. B. Olson for helpful conversations.
PY - 1996/9
Y1 - 1996/9
N2 - Electronic structure calculations were carried out for bcc iron grain boundaries (GB) with or without hydrogen, using the self-consistent Discrete Variational embedded cluster method within the first-principles local density formalism. Bonding characteristics were mainly investigated. Simple rigid body translations perpendicular to the GB plane were used for estimation of relaxed GB geometry. Analysis of bond order summation over the GB shows considerable volume expansion normal to the GB plane of a dense ∑3(111) twist/tilt GB and some compression for the rather open ∑3(110) twist configuration. These results are discussed in the context of atomistic simulations which suggest that higher energy GB's generally have larger volume expansion normal to the GB plane. H in a ∑3(111) GB reduces Fe-Fe bonding strength by ∼3% within a 0.25 nm spherical volume around the H site, associated with reduction of the 4s and 4p occupancy of the nearest neighbor Fe. Since these orbitals contribute mainly to metallic bonding, the action of H atoms as an embrittlement inducer can be understood.
AB - Electronic structure calculations were carried out for bcc iron grain boundaries (GB) with or without hydrogen, using the self-consistent Discrete Variational embedded cluster method within the first-principles local density formalism. Bonding characteristics were mainly investigated. Simple rigid body translations perpendicular to the GB plane were used for estimation of relaxed GB geometry. Analysis of bond order summation over the GB shows considerable volume expansion normal to the GB plane of a dense ∑3(111) twist/tilt GB and some compression for the rather open ∑3(110) twist configuration. These results are discussed in the context of atomistic simulations which suggest that higher energy GB's generally have larger volume expansion normal to the GB plane. H in a ∑3(111) GB reduces Fe-Fe bonding strength by ∼3% within a 0.25 nm spherical volume around the H site, associated with reduction of the 4s and 4p occupancy of the nearest neighbor Fe. Since these orbitals contribute mainly to metallic bonding, the action of H atoms as an embrittlement inducer can be understood.
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U2 - 10.1557/JMR.1996.0281
DO - 10.1557/JMR.1996.0281
M3 - Article
AN - SCOPUS:0030242028
VL - 11
SP - 2214
EP - 2219
JO - Journal of Materials Research
JF - Journal of Materials Research
SN - 0884-2914
IS - 9
ER -