Electronic structure studies and method development for complex materials
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
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.
electronic structure theory, density functional theory
Other Materials Engineering
Research subject Materials Science and Engineering
IdentifiersURN: urn:nbn:se:kth:diva-167109ISBN: 978-91-7595-591-9OAI: oai:DiVA.org:kth-167109DiVA: diva2:813035
2015-06-09, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Udvardi, László, Associate Professor
Vitos, Levente, Professor
QC 201505222015-05-222015-05-212015-05-22Bibliographically approved
List of papers