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Electronic structure studies and method development for complex materials
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Over the years electronic structure theory has proven to be a powerful method with which one can probe the behaviour of materials, making it possible to predict properties that are difficult to measure experimentally. The numerical tools needed for these methods are always in need of development, since the desire to calculate more complex materials pushes this field forward. This thesis contains work on both this implementational and developmental aspects. In the first part we investigate the structural properties of the 6d transition metals using the exact muffin-tin orbitals method. It is found that these elements behave similarly to their lighter counterparts, except for a few deviations. In these cases we argue that it is relativistic effects that cause this anomalous behaviour. In the second part we assess the Padé approximant, which is used in several methods where one wants to include many-body effects into the electronic structure. We point out difficulties that can occur when using this approximant, and propose and evaluate methods for their solution.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , vi, 37 p.
Keyword [en]
electronic structure theory, transition metals, method development
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-118467ISBN: 978-91-7501-646-7 (print)OAI: oai:DiVA.org:kth-118467DiVA: diva2:606386
Presentation
2013-03-07, Konferensrummet, Materialvetenskap, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130219

Available from: 2013-02-19 Created: 2013-02-19 Last updated: 2013-02-19Bibliographically approved
List of papers
1. First-principles calculation of the structural stability of 6d transition metals
Open this publication in new window or tab >>First-principles calculation of the structural stability of 6d transition metals
2011 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 11, 113104- p.Article in journal (Refereed) Published
Abstract [en]

The phase stability of the 6d transition metals (elements 103-111) is investigated using first-principles electronic-structure calculations. Comparison with the lighter transition metals reveals that the structural sequence trend is broken at the end of the 6d series. To account for this anomalous behavior, the effect of relativity on the lattice stability is scrutinized, taking different approximations into consideration. It is found that the mass-velocity and Darwin terms give important contributions to the electronic structure, leading to changes in the interstitial charge density and, thus, in the structural energy difference.

Keyword
crystal-structure, electron-gas
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-41789 (URN)10.1103/PhysRevB.84.113104 (DOI)000294922400001 ()2-s2.0-80053616446 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20111003

Available from: 2011-10-03 Created: 2011-10-03 Last updated: 2017-12-08Bibliographically approved
2. One-particle spectral function and analytic continuation for many-body implementation in the exact muffin-tin orbitals method
Open this publication in new window or tab >>One-particle spectral function and analytic continuation for many-body implementation in the exact muffin-tin orbitals method
2012 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 23, 235107- p.Article in journal (Refereed) Published
Abstract [en]

We investigate one of the most common analytic continuation techniques in condensed matter physics, namely the Pade approximant. Aspects concerning its implementation in the exact muffin-tin orbitals (EMTO) method are scrutinized with special regard towards making it stable and free of artificial defects. The electronic structure calculations are performed for solid hydrogen, and the performance of the analytical continuation is assessed by monitoring the density of states constructed directly and via the Pade approximation. We discuss the difference between the k-integrated and k-resolved analytical continuations, as well as describing the use of random numbers and pole residues to analyze the approximant. It is found that the analytic properties of the approximant can be controlled by appropriate modifications, making it a robust and reliable tool for electronic structure calculations. At the end, we propose a route to perform analytical continuation for the EMTO+dynamical mean field theory method.

Keyword
Approximation
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-109611 (URN)10.1103/PhysRevB.86.235107 (DOI)000312024600001 ()2-s2.0-84871040200 (Scopus ID)
Funder
Swedish Research CouncilEU, European Research Council
Note

QC 20130108

Available from: 2013-01-08 Created: 2013-01-08 Last updated: 2017-12-06Bibliographically approved

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