Following his Trial Lecture on “Machine learning for wavefunction-based electronic structure methods”, Dr. Kristiansen defended his PhD thesis in a purely digital event. The external opponents were Associate Professor Eugene DePrince, Department of Chemistry and Biochemistry, Florida State University, USA, and Professor Sandra Luber, Department of Chemistry, University of Zürich, Switzerland. The administrative leader of the adjudication committee was Associate Professor Jonathan Polfus, Department of Chemistry, University of Oslo, and the Chair of Defence was Professor Harald Walderhaug, Department of Chemistry, University of Oslo.
Dr. Kristiansen’s work was supervised by Professor Thomas Bondo Pedersen (main supervisor), Dr. Simen Kvaal (co-supervisor), and Professor Kenneth Ruud from the Hylleraas Centre for Quantum Molecular Sciences.
Coupled-cluster (CC) theory, often referred to as the gold standard of quantum chemistry, defines a convergent hierarchy of increasingly accurate methods for the description of molecular properties. The same hierarchy of methods can be extended to time-dependent electronic structure theory which is then referred to as time-dependent CC theory (TDCC).
TDCC theory can be formulated with static orbitals or with dynamic orbitals. In his thesis, the candidate has developed software implementing both variants. An assessment of the importance of employing dynamic orbitals is given.