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Hybrid exchange-correlation functional study of the structural, electronic, and mechanical properties of the MAX phases
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. (Condensed Matter Theory Group)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. (Condensed Matter Theory Group)
2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 2, 021902- p.Article in journal (Refereed) Published
Abstract [en]

In this letter, we report on our results obtained with the hybrid functional HSE06 on the structural, electronic, and mechanical properties of the MAX phases. As a sample, we choose Ti2AlN, Ti2AlC, V2AlC, Nb2AlC, Ta2AlC, V2GeC, Ti3SiC2, and Ti4AlN3, which cover all the known types of MAX phases. From our calculations, we have found that V2GeC has the magnetically ordered ground state. Our results are compared to available experimental data, and it is shown that the HSE06 functional can be used as a predictive tool to study the properties of this family of compounds.

Place, publisher, year, edition, pages
2011. Vol. 98, no 2, 021902- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-149784DOI: 10.1063/1.3536513ISI: 000286470800021OAI: oai:DiVA.org:uu-149784DiVA: diva2:405654
Available from: 2011-03-23 Created: 2011-03-23 Last updated: 2017-12-11Bibliographically approved
In thesis
1. 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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Ahuja, Rajeev

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