Investigation of oxidation mechanisms in magnesium by density functional theory
(2025)- Abstract
- Magnesium (Mg) is a metallic material with a great range of potential applications. It can be used as the lightest structure material in automotive and aviation sectors, medical implants, hydrogen storge, etc. In such applications, oxidation and corrosion reactions play a critical role in the effectiveness of use. Therefore, deeper understanding of the fundamental mechanisms of oxidation and corrosion can help in improving the control of fabrication and use of components made of Mg.
In this thesis, my research focused on unravelling the fundamental mechanisms of Mg oxidation at early stages and their dependence on the crystallographic orientation of surface. The work is primarily based on computer simulations using density functional... (More) - Magnesium (Mg) is a metallic material with a great range of potential applications. It can be used as the lightest structure material in automotive and aviation sectors, medical implants, hydrogen storge, etc. In such applications, oxidation and corrosion reactions play a critical role in the effectiveness of use. Therefore, deeper understanding of the fundamental mechanisms of oxidation and corrosion can help in improving the control of fabrication and use of components made of Mg.
In this thesis, my research focused on unravelling the fundamental mechanisms of Mg oxidation at early stages and their dependence on the crystallographic orientation of surface. The work is primarily based on computer simulations using density functional theory (DFT) in open-source code Quantum Espresso (QE). It consists of two major parts with the first part reported in papers I and III, and the second part in Paper II.
In the first part, the initial oxidation mechanisms on the surface of Mg with low-index orientations are investigated theoretically and experimentally. In the experiment, the surface core level shifts (SCLSs) of Mg(0001), Mg(101 ̅0), and Mg(112 ̅0) surfaces were analysed through Mg 2p core level energy spectra in vacuum and non-vacuum environments. For non-vacuum environments, the specimens were exposed to oxygen in the range of 0-4 Langmuir (L) to explore the oxidation process evolution on Mg surfaces. The core level shift values of the Mg 2p caused by different chemical environment obtained in experiment were correlated with spatial atom positions from subsequent DFT simulations. The Mg-O units formed during oxidation on various Mg planes were found to have wurtzite (WZ) structure. The electronic characteristics of Mg clean and oxidized surfaces were then analysed for charge density evolution. I first found that O atoms prefer to adsorb in charge accumulation regions. With the addition of oxygen atoms, the charge environment on the surface becomes redistributed, and subsequent oxygen atoms also follow the rule of adsorbing in the charge accumulation regions. The Mg-O units also have the trend of evolution from WZ to hexagonal MgO phase in geometric configuration during the gradual advancement of oxidation at least up to one monolayer.
In the second part of this thesis, a tailored 2-valence electron pseudopotential of Mg was developed for the DFT simulations of surface interaction phenomena since the evolution of SCLSs is strongly bound to the state of Mg 2p electron energies as the core level. This is at variance to the 10-valence electron pseudopotential more commonly used for Mg. The comparison of our 2-valence electron and the 10-valence electron pseudopotentials carried in paper II proves the former to be sufficiently accurate and thus more efficient for our needs.
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Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/7fe1e6f8-d06e-46a8-b116-d9653e78b1f3
- author
- Xing, Zhe LU
- supervisor
- opponent
-
- Prof. Grönbeck, Henrik, Chalmers University of Technology, Gothenburg.
- organization
- publishing date
- 2025-05-09
- type
- Thesis
- publication status
- published
- subject
- keywords
- Magnesium, Oxidation mechanism, Surface core level shifts (SCLSs), Density functional theory (DFT), Charge Density, Charge accumulationn
- pages
- 62 pages
- publisher
- Department of Industrial and Mechanical Sciences
- defense location
- Lecture Hall M:E, building M, Ole Römers väg 1, Faculty of Engineering LTH, Lund University, Lund.
- defense date
- 2025-05-09 10:15:00
- ISBN
- 978-91-8104-471-3
- 978-91-8104-472-0
- language
- English
- LU publication?
- yes
- id
- 7fe1e6f8-d06e-46a8-b116-d9653e78b1f3
- date added to LUP
- 2025-04-07 11:39:25
- date last changed
- 2025-04-10 11:28:28
@phdthesis{7fe1e6f8-d06e-46a8-b116-d9653e78b1f3,
abstract = {{Magnesium (Mg) is a metallic material with a great range of potential applications. It can be used as the lightest structure material in automotive and aviation sectors, medical implants, hydrogen storge, etc. In such applications, oxidation and corrosion reactions play a critical role in the effectiveness of use. Therefore, deeper understanding of the fundamental mechanisms of oxidation and corrosion can help in improving the control of fabrication and use of components made of Mg.<br/>In this thesis, my research focused on unravelling the fundamental mechanisms of Mg oxidation at early stages and their dependence on the crystallographic orientation of surface. The work is primarily based on computer simulations using density functional theory (DFT) in open-source code Quantum Espresso (QE). It consists of two major parts with the first part reported in papers I and III, and the second part in Paper II.<br/>In the first part, the initial oxidation mechanisms on the surface of Mg with low-index orientations are investigated theoretically and experimentally. In the experiment, the surface core level shifts (SCLSs) of Mg(0001), Mg(101 ̅0), and Mg(112 ̅0) surfaces were analysed through Mg 2p core level energy spectra in vacuum and non-vacuum environments. For non-vacuum environments, the specimens were exposed to oxygen in the range of 0-4 Langmuir (L) to explore the oxidation process evolution on Mg surfaces. The core level shift values of the Mg 2p caused by different chemical environment obtained in experiment were correlated with spatial atom positions from subsequent DFT simulations. The Mg-O units formed during oxidation on various Mg planes were found to have wurtzite (WZ) structure. The electronic characteristics of Mg clean and oxidized surfaces were then analysed for charge density evolution. I first found that O atoms prefer to adsorb in charge accumulation regions. With the addition of oxygen atoms, the charge environment on the surface becomes redistributed, and subsequent oxygen atoms also follow the rule of adsorbing in the charge accumulation regions. The Mg-O units also have the trend of evolution from WZ to hexagonal MgO phase in geometric configuration during the gradual advancement of oxidation at least up to one monolayer.<br/>In the second part of this thesis, a tailored 2-valence electron pseudopotential of Mg was developed for the DFT simulations of surface interaction phenomena since the evolution of SCLSs is strongly bound to the state of Mg 2p electron energies as the core level. This is at variance to the 10-valence electron pseudopotential more commonly used for Mg. The comparison of our 2-valence electron and the 10-valence electron pseudopotentials carried in paper II proves the former to be sufficiently accurate and thus more efficient for our needs.<br/>}},
author = {{Xing, Zhe}},
isbn = {{978-91-8104-471-3}},
keywords = {{Magnesium; Oxidation mechanism; Surface core level shifts (SCLSs); Density functional theory (DFT); Charge Density; Charge accumulationn}},
language = {{eng}},
month = {{05}},
publisher = {{Department of Industrial and Mechanical Sciences}},
school = {{Lund University}},
title = {{Investigation of oxidation mechanisms in magnesium by density functional theory}},
year = {{2025}},
}