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Structural and energetic analysis of the hydrogen storage materials LiNH2BH3 and NaNH2BH3 from ab initio calculations
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science. (Condensed Matter Theory Grp)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science. (Condensed Matter Theory Grp)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science. (Condensed Matter Theory Grp)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science. (Condensed Matter Theory Grp)
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2009 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 13, 132102- p.Article in journal (Refereed) Published
Abstract [en]

Ammonia borane (NH3BH3) possesses many appealing properties as a hydrogen storage material; however, the release of trace amounts of borazine during the desorption process is troublesome. Recently, it was found that substitution of one of the H atoms in the NH3 group by Li or Na could significantly improve the hydrogen desorption properties. The resulting lithium amidoborane (LiNH2BH3) and sodium amidoborane (NaNH2BH3) compounds have been studied by us using density-functional theory. Specifically, we have succeeded in determining the detailed crystal structures of LiNH2BH3 and NaNH2BH3, including the atomic positions in their respective unit cells. Calculated hydrogen removal energies of the hydrogen release reactions are found to be in good agreement with the experimental trend.

Place, publisher, year, edition, pages
2009. Vol. 79, no 13, 132102- p.
Keyword [en]
ab initio calculations, ammonium compounds, boron compounds, crystal structure, density functional theory, desorption, hydrogen storage, lithium compounds, reaction kinetics theory, surface chemistry
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-129060DOI: 10.1103/PhysRevB.79.132102ISI: 000265942800002OAI: oai:DiVA.org:uu-129060DiVA: diva2:337523
Available from: 2010-08-06 Created: 2010-08-05 Last updated: 2017-12-12
In thesis
1. Insights into Materials Properties from Ab Initio Theory: Diffusion, Adsorption, Catalysis & Structure
Open this publication in new window or tab >>Insights into Materials Properties from Ab Initio Theory: Diffusion, Adsorption, Catalysis & Structure
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, density functional theory (DFT) calculations and DFT based ab initio molecular dynamics simulations have been employed in order to gain insights into materials properties like diffusion, adsorption, catalysis, and structure.

In transition metals, absorbed hydrogen atoms self-trap due to localization of metal d-electrons. The self-trapping state is shown to highly influence hydrogen diffusion in the classical over-barrier jump temperature region. Li diffusion in Li-N-H systems is investigated. The diffusion in Li3N is shown to be controlled by the concentration of vacancies. Exchanging one Li for H (Li2NH), gives a system where the diffusion no longer is dependent on the concentrations of vacancies, but instead on N-H rotations. Furthermore, exchanging another Li for H (LiNH2), results in a blockade of Li diffusion. For high-surface area hydrogen storage materials, metal organic frameworks and covalent organic frameworks, the hydrogen adsorption is studied. In metal organic frameworks, a Li-decoration is also suggested as a way to increase the hydrogen adsorption energy. In NaAlH4 doped with transition metals (TM), the hypothesis of TM-Al intermetallic alloys as the main catalytic species is supported. The source of the catalytic effect of carbon nanostructures on hydrogen desorption from NaAlH4 is shown to be the high electronegativity of the carbon nanostructures. A space-group optimized ab initio random structure search method is used to find a new ground state structure for BeC2 and MgC2. The fast change between the amorphous and the crystalline phase of GeSbTe phase-change materials is suggested to be due to the close resemblance between the local amorphous structure and the crystalline structure. Finally, we show that more than 80% of the voltage in the lead acid battery is due to relativistic effects.

 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 81 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 772
Keyword
Density functional theory, Molecular dynamics, Diffusion, Catalysis, Adsorption, Random structure search, Hydrogen-storage materials, Phase-change materials
National Category
Condensed Matter Physics Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-131331 (URN)978-91-554-7907-7 (ISBN)
Public defence
2010-11-12, Siegbansalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Note
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 702Available from: 2010-10-21 Created: 2010-09-30 Last updated: 2011-04-04Bibliographically approved
2. First Principle Studies of Functional Materials: Spintronics, Hydrogen Storage and Cutting Tools
Open this publication in new window or tab >>First Principle Studies of Functional Materials: Spintronics, Hydrogen Storage and Cutting Tools
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The properties of functional materials have been studied with density functional theory.

The first type of materials that have been investigated is the so called diluted magnetic semiconductors. It is a new class of materials that could offer enhanced functionality by making use of spin in addition to the charge of the electron. (Mn,Al) co-doped ZnO has been investigated regarding the Al significance on ferromagnetic behavior using density functional theory within the generalized-gradient approximation plus on-site Coulomb interaction. Despite the presence of Al the system always shows antiferromagnetic behavior. The role of intrinsic defects on ferromagnetism in pure and Cr doped In2O3 was also studied. For pristine In2O3, In vacancy and O interstitial states are completely spin polarized. Moreover, these hole states will create Cr ions in mixed valence state, giving rise to a strong ferromagnetic coupling.

The second type of functional materials studied are hydrogen storage materials for mobile applications. These materials are considered as alternative if hydrogen is to replace fossil fuels as a energy carrier. In the view of this a series of compounds containing boron, nitrogen and hydrogen has been examined with respect to electronic structure, dehydrogenation energy and hydrogen diffusion properties. One compound, NH3BH3, has many desirable properties as a hydrogen storage material. In an effort to improve those properties, one of the H atoms in the NH3 group was replaced by Li, Na or Sr. The calculated hydrogen removal energies of the hydrogen release reactions were found to be significantly improved.

Finally, a coating material, Al2O3, for wear resistant coatings on high performance cemented carbide cutting tools has been investigated. Chemical vapor deposition grown Al2O3 has been used for decades by the industry. To improve the growth process H2S is added to the gas mixture. The catalytic effect of H2S on the AlCl3/H2/CO2/HCl chemical vapor deposition process has been investigated on an atomistic scale. By applying a combined approach of thermodynamic modeling and density functional theory it seems that H2S acts as mediator for the oxygenation of the Al-surface which will in turn increase the growth rate of Al2O3.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 60 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 871
Keyword
spintronics, hydrogen storage, coating materials
National Category
Natural Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-160270 (URN)978-91-554-8191-9 (ISBN)
Public defence
2011-12-02, Siegbahnsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2011-11-11 Created: 2011-10-19 Last updated: 2011-11-23Bibliographically approved
3. Structural, Electronic and Mechanical Properties of Advanced Functional Materials
Open this publication in new window or tab >>Structural, Electronic and Mechanical Properties of Advanced Functional Materials
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The search for alternate and renewable energy resources as well as the efficient use of energy and development of such systems that can help to save the energy consumption is needed because of exponential growth in world population, limited conventional fossil fuel resources, and to meet the increasing demand of clean and environment friendly substitutes. Hydrogen being the simplest, most abundant and clean energy carrier has the potential to fulfill some of these requirements provided the development of efficient, safe and durable systems for its production, storage and usage.

Chemical hydrides, complex hydrides and nanomaterials, where the hydrogen is either chemically bonded to the metal ions or physiosorbed, are the possible means to overcome the difficulties associated with the storage and usage of hydrogen at favorable conditions. We have studied the structural and electronic properties of some of the chemical hydrides, complex hydrides and functionalized nanostructures to understand the kinetics and thermodynamics of these materials.

Another active field relating to energy storage is rechargeable batteries. We have studied the detailed crystal and electronic structures of Li and Mg based cathode materials and calculated the average intercalation voltage of the corresponding batteries. We found that transition metal doped MgH2 nanocluster is a material to use efficiently not only in batteries but also in fuel-cell technologies.

MAX phases can be used to develop the systems to save the energy consumption. We have chosen one compound from each of all known types of MAX phases and analyzed the structural, electronic, and mechanical properties using the hybrid functional. We suggest that the proper treatment of correlation effects is important for the correct description of Cr2AlC and Cr2GeC by the good choice of Hubbard 'U' in DFT+U method.

Hydrogen is fascinating to physicists due to predicted possibility of metallization and high temperature superconductivity. On the basis of our ab initio molecular dynamics studies, we propose that the recent claim of conductive hydrogen by experiments might be explained by the diffusion of hydrogen at relevant pressure and temperature.

In this thesis we also present the studies of phase change memory materials, oxides and amorphization of oxide materials, spintronics and sulfide materials.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 98 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1062
Keyword
DFT, Hydrogen storage, Rechargeable batteries, Amorphization, Electronic structure, Crystal strcuture, Molecular dynamics, Diffusion, Intercalation voltage, High pressure, MAX phases, Mechanical properties, Optical properties, Phase change memory, Spintronics, Magnetism, Correlation effects, Band structure
National Category
Physical Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-205243 (URN)978-91-554-8723-2 (ISBN)
Public defence
2013-09-27, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2013-09-06 Created: 2013-08-15 Last updated: 2014-01-08Bibliographically approved

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Ramzan, MuhammadScheicher, Ralph H.Ahuja, Rajeev

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