Aleksei V. Ivanov defended his doctoral thesis Calculations of Ground and Excited Electronic States Using Self-Interaction Corrected Density Functionals on April 9 2021.
Opponents at the defence were Thomas Olsen, Associate Professor at the Department of Physics, Technical University of Denmark and Andrei Manolescu, Professor at the School of Technology, Department of Engineering, Reykjavik University.
The advisor of Aleksei was Hannes Jónsson, Professor at the Faculty of Physical Sciences, University of Iceland. Other members of the doctoral committee were Egill Skúlason, Professor at the Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland and Elvar Örn Jónsson, Specialist at the Science Institute, University of Iceland.
Dr. Einar Örn Sveinbjörnsson, Professor and the Head of the Faculty of Physical Sciences, University of Iceland was the Chair of Ceremony.
Direct optimization methods for the calculation of ground and excited electronic states are presented for both total density and orbital-density-dependent functionals. The methods have been developed for various types of basis sets including localized atomic orbitals, plane waves and real space grid. The algorithms have been implemented in combination with the projector-augmented-wave method to represent inner electrons of the atoms. The direct optimization method is shown to be more robust and faster than the conventional self-consistent field approach in calculations of both ground and excited states. An assessment of the Perdew-Zunger self-interaction correction (PZ-SIC) to the energy functional has also been made and its performance compared to the commonly used generalized gradient approximation (GGA). PZ-SIC is found to systematically improve the description of the atomization and ionization energy as well as the band gaps of insulators, but needs to be scaled by a half. PZ-SIC can be especially important for the accurate description of systems containing transition metals as is illustrated by the excellent results obtained for the Mn dimer, a system where results of GGA calculations are qualitatively incorrect. However, PZ-SIC does not substantially improve the excitation energy of small organic molecules as the correction there tends to cancel out when the energy of ground and excited states is compared. The efficient and practical implementation of PZ-SIC presented here paves the way for the development of more accurate orbital-density-dependent functionals.