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Structural, magnetic, and energetic properties of Na2FePO4F, Li2FePO4F, NaFePO4F, and LiFePO4F from ab initio calculations
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
Laboratorie de Cristallographie, Résonance Magnétique et Modélisations, Institut Jean Barriol, Nancy Université.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
2009 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, no 4, 043510- p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we report on Na2FePO4F and Li2FePO4F, which are materials that are used as cathodes in batteries, using density functional theory with the LDA, LDA + U, GGA, or GGA + U approximations. Specifically, we study their crystal structure, electronic structure, and magnetic properties and provide similar information about the intermediate compounds LiFePO4F and NaFePO4F. Finally, the intercalation voltages of the corresponding batteries are calculated using various exchange-correlation approximations and conclusions are drawn about which one is the most suitable to use for the study of this class of materials.

Place, publisher, year, edition, pages
American Institute of Physics , 2009. Vol. 106, no 4, 043510- p.
National Category
Physical Sciences
Research subject
Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-108262DOI: 10.1063/1.3202384ISI: 000270083800025OAI: oai:DiVA.org:uu-108262DiVA: diva2:234797
Available from: 2009-09-10 Created: 2009-09-10 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Computational Studies of Nanotube Growth, Nanoclusters and Cathode Materials for Batteries
Open this publication in new window or tab >>Computational Studies of Nanotube Growth, Nanoclusters and Cathode Materials for Batteries
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Density functional theory has been used to investigate cathode materials for rechargeable batteries, carbon nanotube interactions with catalyst particles and transition metal catalyzed hydrogen release in magnesium hydride nanoclusters.

An effort has been made to the understand structural and electrochemical properties of lithium iron silicate (Li2FeSiO4) and its manganese-doped analogue. Starting from the X-ray measurements, the crystal structure of Li2FeSiO4 was refined, and several metastable phases of partially delithiated Li2FeSiO4 were identified. There are signs that manganese doping leads to structural instability and that lithium extraction beyond 50% capacity only occurs at impractically high potentials in the new material.

The chemical interaction energies of single-walled carbon nanotubes and nanoclusters were calculated. It is found that the interaction needs to be strong enough to compete with the energy gained by detaching the nanotubes and forming closed ends with carbon caps. This represents a new criterion for determining catalyst metal suitability. The stability of isolated carbon nanotube fragments were also studied, and it is argued that chirality selection during growth is best achieved by exploiting the much wider energy span of open-ended carbon nanotube fragments.

Magnesium hydride nanoclusters were doped with transition metals Ti, V, Fe, and Ni. The resulting changes in hydrogen desorption energies from the surface were calculated, and the associated changes in the cluster structures reveal that the transition metals not only lower the desorption energy of hydrogen, but also seem to work as proposed in the gateway hypothesis of transition metal catalysis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 59 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 670
Keyword
Materials science, density functional theory, cathode materials, hydrogen-storage materials, carbon nanotube growth
National Category
Other Physics Topics
Research subject
Physics of Matter; Materials Science
Identifiers
urn:nbn:se:uu:diva-108261 (URN)978-91-554-7603-8 (ISBN)
Public defence
2009-10-23, Polhemsalen, Ångströmlaboratoriet, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2009-10-01 Created: 2009-09-10 Last updated: 2009-10-01
2. 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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