Séminaire de l'équipe PCMT: Marios-Petros Kitsaras (LCPQ@Toulouse, France)

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From Magnetic Fields to Ionization Potentials and Beyond

Electronic structure theory is a cornerstone of modern theoretical chemistry, providing a qualitative and quantitative description of chemical bonding and molecular properties. It enables the investigation of chemical phenomena in environments that are difficult to reproduce experimentally, such as the interstellar medium or the atmospheres of magnetic White Dwarf stars. It also plays an important role in addressing contemporary challenges, from the development of energy materials to understanding the chemical processes occurring in Earth's atmosphere.

In the first part of the presentation, I will present advances in highly accurate quantum-chemical methods for studying atoms and molecules in strong magnetic fields, with applications to the interpretation of spectra from magnetic White Dwarf stars [1-3]. These investigations rely on Coupled-Cluster theory, one of the most accurate families of ab initio electronic-structure methods currently available. 

The second part of the presentation focuses on Green's function methods, which combine accuracy with computational efficiency for the prediction of charged excitations, such as ionization energies and electron affinities, as well as electronically excited states. I will present the recently established connection between Green's function methods and Coupled-Cluster theory [4]. This framework extends Green's function methods beyond vertical electronic processes, enabling the description of electronic properties along structural distortions and opening the way to the prediction of adiabatic molecular properties.5 More broadly, it opens new avenues for systematically improving the predictive accuracy of Green's function methods while retaining their computational efficiency. Although these two topics address distinct physical problems, they share the common objective of developing predictive electronic-structure methods that bridge theory and experiment by enabling the interpretation of increasingly sophisticated spectroscopic observations and complex chemical phenomena.

(1) Hollands, M. A.; Stopkowicz, S.; Kitsaras, M.-P.; Hampe, F.; Blaschke, S.; Hermes, J. J. Mon. Not. R. Astron. Soc. 2023, 520 (3), 3560–3575. https://doi.org/10.1093/mnras/stad143.

(2) Kitsaras, M.-P.; Grazioli, L.; Stopkowicz, S. J. Chem. Phys. 2024, 160 (9), 094112. https://doi.org/10.1063/5.0189350.

(3) Kitsaras, M.-P.; Hampe, F.; Reimund, L.; Stopkowicz, S. J. Chem. Theory Comput. 2025, 21 (20), 10177–10192. https://doi.org/10.1021/acs.jctc.5c00779.

(4) Tölle, J.; Kitsaras, M.-P.; Irmler, A.; Grüneis, A.; Loos, P.-F. J. Chem. Theory Comput. 2026, 22 (13), 6471–6486. https://doi.org/10.1021/acs.jctc.6c00378.

(5) Kitsaras, M.-P.; Tölle, J.; Loos, P.-F. J. Chem. Phys. 2026, 164 (4). https://doi.org/10.1063/5.0309945.