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Ab initio based modeling of defects and disorder in industrial materials
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The study of defects and disorder in condensed matter remains a central subject of materials science. Newly emerging experimental and theoretical techniques promote our understanding in this field, and reveal many interesting phenomena in which the atomic picture plays a crucial role. In this thesis we present a study on the fundamental and applied aspects of defects and disorder in industrial materials.

We consider the basic aspects of defective and disordered crystals, and discuss the structural, electronic, thermodynamic and mechanical properties of such materials. In particular, we have systematically investigated the defects in copper metal based on ab initio calculations. The point defects, point defects interactions, stacking faults, and the grain boundaries have been studied. Efforts are made to relate the atomistic information to the macroscopic mechanical behavior of copper metal possessing defects. The stackingfault energy of copper is found to be sensitive to the change of temperature and the presence of point defects. The atomic size effect of phosphorous is more evident for the change of the stacking-fault energy of copper among the 3sp impurities. While the change of the work of separation of grain boundary is found to follow the pattern of the chemical effect. When the chemical effect dominates, the impurity enhances the cohesion strength of grain boundary, and vice versa. The study well explains the various influence of the defects on the macroscopic mechanical properties of copper, including the anomalous behaviour of phosphorous in copper.

The structure and properties of monovalent copper compounds with oxygen and/or hydrogen were also explored. The ground-state cuprice–CuOH(s) was identified using a combined theoretical-experimental effort. The structure determined with DFT was validated by comparison with the X-ray diffraction data obtained from the synthesized material. The ground-state structure of CuOH(s) has a layered structure that is stabilized by antiferroelectric cation ordering which, in turn, is caused by collective electrostatic interactions. The electronic and thermodynamic properties of the cationordered CuOH(s) are intimately linked to the bonding topology in this material, which is composed of one-dimensional (folded and interlocked chains) and two-dimensional (layers) structural units. The solid CuOH is an indirect band gap semiconductor, while the band gap varies between 2.73 eV and 3.03 eV due to cation disorder. The hydrogen in CuOH has little effect on the ionic nature of the Cu–O bonding relative to that in Cu2O, but lowers the energy levels of the occupied states by giving a covalent character to the O–H bond. The competing structures of copper hydride were also investigated. Structure–property relationships were analyzed on this series of materials to gain fundamental understanding of their behaviour.

Defects and disorder are also important for understanding the structure γ-alumina. Our calculations have confirmed that the most stable structure of γ-alumina is the defective spinel phase with disordered cation vacancies. The hydrogenated spinel phase is also dynamically stable, but thermodynamically unstable with respect to the defective spinel phase and H2O, as well as relative to the defective spinel phase and Boehmite (γ- AlO(OH)). This is in spite of the high entropy content of hydrogenated γ-alumina. Our calculations and analysis allow us to conclude that the hydrogenated spinel structure is only a metastable phase that forms during the decomposition of Boehmite above 753 K. However, dehydration of the metastable phase into the ground state is expected to be a slow process due to the low diffusion rate of H, which leaves hydrogen as a locked-in impurity in γ-alumina under conditions of normal temperature and pressure.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , viii, 93 p.
National Category
Condensed Matter Physics
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-170617ISBN: 978-91-7595-640-4 (print)OAI: oai:DiVA.org:kth-170617DiVA: diva2:839147
Public defence
2015-08-28, Sal E2,, Lindstedtvägen 3, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Radiation Safety Authority
Note

QC 20150813

Available from: 2015-08-13 Created: 2015-07-01 Last updated: 2015-08-13Bibliographically approved
List of papers
1. Interactions of point defects with stacking faults in oxygen-free phosphorus-containing copper
Open this publication in new window or tab >>Interactions of point defects with stacking faults in oxygen-free phosphorus-containing copper
2015 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 462, 160-164 p.Article in journal (Refereed) Published
Abstract [en]

The interactions of stacking faults and point defects in oxygen-free phosphorus-containing copper are investigated using ab initio methods. Although monovacancies can act as traps for H impurities or OH groups, the calculations show that two vacancies only weakly bind with each other and this interaction terminates at the third nearest-neighbor distance. An interstitial P tends to form a Cu-P dumbbell-like cluster around the lattice site and can readily combine with a vacancy to become a substitutional impurity. It is also found that the intrinsic stacking-fault energy of copper strongly depends on the temperature as well as on the presences of point defects. The intrinsic stacking-fault energy varies between 20 and 77 mJ/m2 depending on the presence of point defects in the faulted region. These point defects are also found to affect the unstable stacking-fault energy, but they always increase the twinning tendency of copper. Among them, the substitutional P is found to have the strongest effects, decreasing the intrinsic stacking-fault energy and increasing the twinnability.

Keyword
Calculations, Copper, Impurities, Oxygen, Phosphorus, Point defects, Substitution reactions, Vacancies, Ab initio method, Dumbbell likes, Intrinsic stacking fault, Lattice sites, Monovacancies, Nearest neighbor distance, Stacking fault energies, Substitutional impurities
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-166923 (URN)10.1016/j.jnucmat.2015.03.041 (DOI)000357545900018 ()2-s2.0-84927137336 (Scopus ID)
Funder
Swedish Foundation for Strategic Research
Note

QC 20150609

Available from: 2015-06-09 Created: 2015-05-21 Last updated: 2017-12-04Bibliographically approved
2. Defect Chemistry and Ductile-to-brittle Transition in Polycrystalline Cu Metal
Open this publication in new window or tab >>Defect Chemistry and Ductile-to-brittle Transition in Polycrystalline Cu Metal
(English)Manuscript (preprint) (Other academic)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-172104 (URN)
Note

QS 2015

Available from: 2015-08-12 Created: 2015-08-12 Last updated: 2015-08-13Bibliographically approved
3. Bonding Topology and Antiferroelectric Order in Cuprice, CuOH
Open this publication in new window or tab >>Bonding Topology and Antiferroelectric Order in Cuprice, CuOH
(English)Manuscript (preprint) (Other academic)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-172111 (URN)
Note

QC 20160613

Available from: 2015-08-13 Created: 2015-08-13 Last updated: 2016-06-13Bibliographically approved
4. Physcico-chemical Properties of Cu(I) Compounds with O and/or H
Open this publication in new window or tab >>Physcico-chemical Properties of Cu(I) Compounds with O and/or H
(English)Manuscript (preprint) (Other academic)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-172114 (URN)
Note

QS 2015

Available from: 2015-08-13 Created: 2015-08-13 Last updated: 2015-08-13Bibliographically approved
5. Electronic structures and optical properties of cuprous oxide and hydroxide
Open this publication in new window or tab >>Electronic structures and optical properties of cuprous oxide and hydroxide
2014 (English)In: Materials Research Society Symposium Proceedings, ISSN 0272-9172, E-ISSN 1946-4274, Vol. 1675, 185-190 p.Article in journal (Refereed) Published
Abstract [en]

The broad range of applications of copper, including areas such as electronics, fuel cells, and spent nuclear fuel disposal, require accurate description of the physical and chemical properties of copper compounds. Within some of these applications, cuprous hydroxide is a compound whose relevance has been recently discovered. Its existence in the solid-state form was recently reported. Experimental determination of its physical-chemical properties is challenging due to its instability and poop crystallinity. Within the framework of density functional theory calculations (DFT), we investigated the nature of bonding, electronic spectra, and optical properties of the cuprous oxide and cuprous hydroxide. It is found that the hybrid functional PBEO can accurately describe the electronic structure and optical properties of these two copper(I) compounds. The calculated properties of cuprous oxide are in good agreement with the experimental data and other theoretical results. The structure of cuprous hydroxide can be deduced from that of cuprous oxide by substituting half Cu∗ in Cu2O lattice with protons. Compared to CU2O, the presence of hydrogen in CuOH has little effect on the ionic nature of Cu-O bonding, but lowers the energy levels of the occupied states. Thus, CuOH is calculated to have a wider indirect band gap of 2.73 eV compared with the Cu2O band gap of 2.17 eV.

Keyword
Chemical bonds, Chemical compounds, dioactive wastes
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-168526 (URN)10.1557/opl.2014.862 (DOI)2-s2.0-84922434279 (Scopus ID)
Conference
2014 MRS Spring Meeting; San Francisco; United States
Note

QC 20150609

Available from: 2015-06-09 Created: 2015-06-04 Last updated: 2017-12-04Bibliographically approved
6. Cation Ordering in Cuprice, CuOH
Open this publication in new window or tab >>Cation Ordering in Cuprice, CuOH
2015 (English)In: Proceedings of PTM 2015, 2015Conference paper, Published paper (Other academic)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-172112 (URN)2-s2.0-84962734564 (Scopus ID)
Conference
International Conference on Solid Phase Transformations in Inorganic Materials, Canada 2015
Note

NQC 201508

Available from: 2015-08-13 Created: 2015-08-13 Last updated: 2015-08-13Bibliographically approved
7. The nature of hydrogen in gamma-alumina
Open this publication in new window or tab >>The nature of hydrogen in gamma-alumina
2014 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 20, 203514- p.Article in journal (Refereed) Published
Abstract [en]

Gibbs free energy models are derived from the calculated electronic and phonon structure of two possible models of gamma-alumina, a defective spinel phase and a hydrogenated spinel phase. The intrinsic vacancies and hydrogen in the two structural models give rise to a considerable configurational (residual) entropy and significantly contribute to thermodynamic stability and physical-chemical properties of gamma-alumina, which was neglected in previous studies but considered in this work. The electronic densities of states, calculated using a hybrid functional for the two structural models of gamma-alumina, are presented. The dynamic stability of the two phases is confirmed by full-spectrum phonon calculations. The two phases share many similarities in their electronic structure, but can be distinguished by their vibrational spectra and specific heat. The defective spinel is found to be the ground state of gamma-alumina, while the hydrogenated spinel to be a metastable phase. However, dehydration of the metastable phase into the ground state is expected to be slow due to the low diffusion rate of H, which leaves hydrogen as a locked-in impurity in gamma-alumina.

National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-147960 (URN)10.1063/1.4879897 (DOI)000337143500030 ()2-s2.0-84901989640 (Scopus ID)
Note

QC 20140711

Available from: 2014-07-11 Created: 2014-07-10 Last updated: 2017-12-05Bibliographically approved

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