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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.
2015 (English)Doctoral 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 describe and predict material properties. 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.

It begins by reviewing density functional theory and dynamical mean field theory, with the aim of merging these two methods. We point out theoretical and technical issues that may occur while doing this. One issue is the Padé approximant, which is used for analytical continuation. We assess the approximant and point out difficulties that can occur, and propose and evaluate methods for their solution.

The virial theorem is assessed within the framework of density functional theory merged with many-body methods. We find that the virial theorem is extended from its usual form, and confirm this by performing practical calculations.

The unified theory of crystal structure for transition metals has been established a long time ago using early electronic structure calculations. Here we implement the first- principles exact muffin-tin orbitals method to investigate the structural properties of the 6d transition metals. The goal of our study is to verify the existing theory for the mostly unknown 6d series and the performance of the current state-of-the art in the case of heavy d metals. 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. Palladium is then studied, taking many-body effects into account. We find that we can reproduce experimental photoemission spectra by these methods, as well as the Fermi surface.

The thesis ends with an investigation of the stacking fault energies of the strongly correlated metal cerium. In addition to providing the first ab-initio stacking fault data for the two cubic phases of Ce, we discuss how these results could have an impact on the interpretation of the phase diagram of cerium

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , 92 p.
Keyword [en]
electronic structure theory, density functional theory
National Category
Other Materials Engineering
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-167109ISBN: 978-91-7595-591-9 (print)OAI: oai:DiVA.org:kth-167109DiVA: diva2:813035
Public defence
2015-06-09, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150522

Available from: 2015-05-22 Created: 2015-05-21 Last updated: 2015-05-22Bibliographically approved
List of papers
1. 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
2. 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
3. Origin of β-cerium investigated with ab initio calculations of stacking fault energies
Open this publication in new window or tab >>Origin of β-cerium investigated with ab initio calculations of stacking fault energies
(English)Manuscript (preprint) (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-167138 (URN)
Note

QS 2015

Available from: 2015-05-21 Created: 2015-05-21 Last updated: 2015-05-22Bibliographically approved
4. The virial theorem within many-body extensions of density functional theory
Open this publication in new window or tab >>The virial theorem within many-body extensions of density functional theory
(English)Manuscript (preprint) (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-167141 (URN)
Note

QS 2015

Available from: 2015-05-21 Created: 2015-05-21 Last updated: 2015-05-22Bibliographically approved
5. The electronic structure of palladium in the presence of many-body effects
Open this publication in new window or tab >>The electronic structure of palladium in the presence of many-body effects
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-167142 (URN)
Note

QS 2015

Available from: 2015-05-21 Created: 2015-05-21 Last updated: 2015-05-22Bibliographically approved
6. Transmission through correlated CunCoCun heterostructures
Open this publication in new window or tab >>Transmission through correlated CunCoCun heterostructures
Show others...
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 5, 054431Article in journal (Refereed) Published
Abstract [en]

We propose a method to compute the transmission through correlated heterostructures by combining density functional and many-body dynamical mean field theories. The heart of this combination consists in porting the many-body self-energy from an all electron basis into a pseudopotential localized atomic basis set. Using this combination we study the effects of local electronic interactions and finite temperatures on the transmission across the Cu4CoCu4 metallic heterostructure. It is shown that as the electronic correlations are taken into account via a local but dynamic self-energy, the total transmission at the Fermi level gets reduced (predominantly in the minority-spin channel), whereby the spin polarization of the transmission increases. The latter is due to a more significant d-electron contribution, as compared to the noncorrelated case in which the transport is dominated by s and p electrons.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-167143 (URN)10.1103/PhysRevB.92.054431 (DOI)000362210600005 ()2-s2.0-84941085962 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, 618082Swedish Research Council
Note

QC 20151102. Updated from manuscript to article in journal.

Available from: 2015-05-21 Created: 2015-05-21 Last updated: 2017-12-04Bibliographically approved

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