Surface atomic relaxation and magnetism on hydrogen-adsorbed Fe(110) surfaces from first principles

Urslaan K. Chohan; Enrique Jimenez-Melero; Sven P.K. Koehler

doi:10.1016/j.apsusc.2016.06.027

Surface atomic relaxation and magnetism on hydrogen-adsorbed Fe(110) surfaces from first principles

Urslaan K. Chohan
, Enrique Jimenez-Melero
, Sven P.K. Koehler^*

^*Corresponding author for this work

Metallurgy and Materials

Research output: Contribution to journal › Article › peer-review

Abstract

We have computed adsorption energies, vibrational frequencies, surface relaxation and buckling for hydrogen adsorbed on a body-centred-cubic Fe(110) surface as a function of the degree of H coverage. This adsorption system is important in a variety of technological processes such as the hydrogen embrittlement in ferritic steels, which motivated this work, and the Haber–Bosch process. We employed spin-polarised density functional theory to optimise geometries of a six-layer Fe slab, followed by frozen mode finite displacement phonon calculations to compute Fe–H vibrational frequencies. We have found that the quasi-threefold (3f) site is the most stable adsorption site, with adsorption energies of ∼3.0 eV/H for all coverages studied. The long-bridge (lb) site, which is close in energy to the 3f site, is actually a transition state leading to the stable 3f site. The calculated harmonic vibrational frequencies collectively span from 730 to 1220 cm ⁻¹ , for a range of coverages. The increased first-to-second layer spacing in the presence of adsorbed hydrogen, and the pronounced buckling observed in the Fe surface layer, may facilitate the diffusion of hydrogen atoms into the bulk, and therefore impact the early stages of hydrogen embrittlement in steels.

Original language	English
Pages (from-to)	385-392
Number of pages	8
Journal	Applied Surface Science
Volume	387
DOIs	https://doi.org/10.1016/j.apsusc.2016.06.027
Publication status	Published - 30 Nov 2016

Bibliographical note

Funding Information:
We gratefully acknowledge the financial support of the Engineering and Physical Sciences Research Council UK ( EPSRC ) through the Centre for Doctoral Training in Advanced Metallic Systems. We thank the Dalton Cumbrian Facility for providing funding to cover the cost of the computational time, and also the Computational Shared Facility at The University of Manchester, in particular to Pen Richardson. We thank Christopher Lee for helpful discussions.

Publisher Copyright:
© 2016 Elsevier B.V.

Keywords

Adsorption
Density functional theory
Ferritic steels
Haber–Bosch process
Hydrogen embrittlement

ASJC Scopus subject areas

General Chemistry
Condensed Matter Physics
General Physics and Astronomy
Surfaces and Interfaces
Surfaces, Coatings and Films

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10.1016/j.apsusc.2016.06.027

Cite this

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title = "Surface atomic relaxation and magnetism on hydrogen-adsorbed Fe(110) surfaces from first principles",

abstract = " We have computed adsorption energies, vibrational frequencies, surface relaxation and buckling for hydrogen adsorbed on a body-centred-cubic Fe(110) surface as a function of the degree of H coverage. This adsorption system is important in a variety of technological processes such as the hydrogen embrittlement in ferritic steels, which motivated this work, and the Haber–Bosch process. We employed spin-polarised density functional theory to optimise geometries of a six-layer Fe slab, followed by frozen mode finite displacement phonon calculations to compute Fe–H vibrational frequencies. We have found that the quasi-threefold (3f) site is the most stable adsorption site, with adsorption energies of ∼3.0 eV/H for all coverages studied. The long-bridge (lb) site, which is close in energy to the 3f site, is actually a transition state leading to the stable 3f site. The calculated harmonic vibrational frequencies collectively span from 730 to 1220 cm −1 , for a range of coverages. The increased first-to-second layer spacing in the presence of adsorbed hydrogen, and the pronounced buckling observed in the Fe surface layer, may facilitate the diffusion of hydrogen atoms into the bulk, and therefore impact the early stages of hydrogen embrittlement in steels.",

keywords = "Adsorption, Density functional theory, Ferritic steels, Haber–Bosch process, Hydrogen embrittlement",

author = "Chohan, \{Urslaan K.\} and Enrique Jimenez-Melero and Koehler, \{Sven P.K.\}",

note = "Funding Information: We gratefully acknowledge the financial support of the Engineering and Physical Sciences Research Council UK ( EPSRC ) through the Centre for Doctoral Training in Advanced Metallic Systems. We thank the Dalton Cumbrian Facility for providing funding to cover the cost of the computational time, and also the Computational Shared Facility at The University of Manchester, in particular to Pen Richardson. We thank Christopher Lee for helpful discussions. Publisher Copyright: {\textcopyright} 2016 Elsevier B.V.",

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doi = "10.1016/j.apsusc.2016.06.027",

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AU - Chohan, Urslaan K.

AU - Jimenez-Melero, Enrique

AU - Koehler, Sven P.K.

N1 - Funding Information: We gratefully acknowledge the financial support of the Engineering and Physical Sciences Research Council UK ( EPSRC ) through the Centre for Doctoral Training in Advanced Metallic Systems. We thank the Dalton Cumbrian Facility for providing funding to cover the cost of the computational time, and also the Computational Shared Facility at The University of Manchester, in particular to Pen Richardson. We thank Christopher Lee for helpful discussions. Publisher Copyright: © 2016 Elsevier B.V.

PY - 2016/11/30

Y1 - 2016/11/30

N2 - We have computed adsorption energies, vibrational frequencies, surface relaxation and buckling for hydrogen adsorbed on a body-centred-cubic Fe(110) surface as a function of the degree of H coverage. This adsorption system is important in a variety of technological processes such as the hydrogen embrittlement in ferritic steels, which motivated this work, and the Haber–Bosch process. We employed spin-polarised density functional theory to optimise geometries of a six-layer Fe slab, followed by frozen mode finite displacement phonon calculations to compute Fe–H vibrational frequencies. We have found that the quasi-threefold (3f) site is the most stable adsorption site, with adsorption energies of ∼3.0 eV/H for all coverages studied. The long-bridge (lb) site, which is close in energy to the 3f site, is actually a transition state leading to the stable 3f site. The calculated harmonic vibrational frequencies collectively span from 730 to 1220 cm −1 , for a range of coverages. The increased first-to-second layer spacing in the presence of adsorbed hydrogen, and the pronounced buckling observed in the Fe surface layer, may facilitate the diffusion of hydrogen atoms into the bulk, and therefore impact the early stages of hydrogen embrittlement in steels.

AB - We have computed adsorption energies, vibrational frequencies, surface relaxation and buckling for hydrogen adsorbed on a body-centred-cubic Fe(110) surface as a function of the degree of H coverage. This adsorption system is important in a variety of technological processes such as the hydrogen embrittlement in ferritic steels, which motivated this work, and the Haber–Bosch process. We employed spin-polarised density functional theory to optimise geometries of a six-layer Fe slab, followed by frozen mode finite displacement phonon calculations to compute Fe–H vibrational frequencies. We have found that the quasi-threefold (3f) site is the most stable adsorption site, with adsorption energies of ∼3.0 eV/H for all coverages studied. The long-bridge (lb) site, which is close in energy to the 3f site, is actually a transition state leading to the stable 3f site. The calculated harmonic vibrational frequencies collectively span from 730 to 1220 cm −1 , for a range of coverages. The increased first-to-second layer spacing in the presence of adsorbed hydrogen, and the pronounced buckling observed in the Fe surface layer, may facilitate the diffusion of hydrogen atoms into the bulk, and therefore impact the early stages of hydrogen embrittlement in steels.

KW - Adsorption

KW - Density functional theory

KW - Ferritic steels

KW - Haber–Bosch process

KW - Hydrogen embrittlement

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DO - 10.1016/j.apsusc.2016.06.027

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JO - Applied Surface Science

JF - Applied Surface Science

ER -

Surface atomic relaxation and magnetism on hydrogen-adsorbed Fe(110) surfaces from first principles

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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