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Role of correlation and relativistic effects in MAX phases
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
2012 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 47, no 21, 7615-7620 p.Article in journal (Refereed) Published
Abstract [en]

We have performed the ab initio calculations to study the role of correlation and relativistic effects in MAX phases. As of now, there are more than 50 MAX phases reported in the literature; however, we have chosen two MAX phases, namely Cr2AlC and Ta2AlC, as representatives of MAX phases for our study as they are very poorly described from calculation point of view. Our results show that correlation effects are very important to understand the electronic and mechanical properties of Cr2AlC, but not so important for Ta2AlC. We have also studied the relativistic effects on Ta2AlC and our calculations show that going from scalar to fully relativistic effects does not have any significant effect on the electronic and mechanical properties of Ta2AlC. We conclude that Ta2AlC is a weakly correlated system, whereas Cr2AlC is a strongly correlated system. Further experiments are needed to explain the discrepancy between theory and experiments.

Place, publisher, year, edition, pages
2012. Vol. 47, no 21, 7615-7620 p.
Keyword [en]
Generalized Gradient Approximation, Initio Molecular-Dynamics, Band-Structure, Ti3sic2, Cr, Transition, Solids, Ta2alc, Energy, Ta
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-102336DOI: 10.1007/s10853-012-6609-6ISI: 000307520900026Scopus ID: 2-s2.0-84865248947OAI: oai:DiVA.org:kth-102336DiVA: diva2:552491
Funder
Swedish Research Council
Note

QC 20120914

Available from: 2012-09-14 Created: 2012-09-14 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Heavy Metal Compounds and Hydrogen Storage Materials from Ab Initio Calculations
Open this publication in new window or tab >>Heavy Metal Compounds and Hydrogen Storage Materials from Ab Initio Calculations
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In principle, most of the properties of solids can be determined by their electronic structures. So the understanding of electronic structures is essential. This thesis presents two classes of materials using ab initio method based on density functional theory. One is heavy metal compounds like Ta2AlC, ThO and the other one is hydrogen storage material namely MgH2 surfaces.

The study of correlation and relativistic effects in Ta2AlC are presented. Based on our results, Ta2AlC is a weakly correlated system. Our study shows that the spin - orbital coupling does not play a very important role where as the other relativistic corrections such as mass velocity and Darwin terms have a significant effect on the electronic properties.

The stability of rock salt like ThO has been proposed based on the first principle calculation. ThO can be stabilized under pressure. The driving force is the sd to f charge transfer in Th.

We have investigated the energetics of hydrogen desorption from the MgH2 (110) and (001) surfaces. The doping of foreign metal elements and strain were used to reduce the dehydrogenation energy. The reduction in dehydrogenation energy is caused by the charge localization on the metal atoms which leads to destabilization and the weakening of metal - hydrogen bonds.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. vii, 32 p.
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-120062 (URN)978-91-7501-675-7 (ISBN)
Presentation
2013-04-10, Sal M131, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130327

Available from: 2013-03-27 Created: 2013-03-27 Last updated: 2013-03-27Bibliographically approved

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