Contact

Clara Lisa E Silva


Phone: +33 476 88 2044

Ph.D. projects

Fundamentals of f-electron systems by X-ray advanced spectroscopies

Ph.D. student:

Clara Lisa E Silva

Supervisor:

Prof. Dr. Kristina Kvashnina (HZDR, University Grenoble Alpes), Dr. Lucia Amidani (HZDR)

Department:

Molecular Structures

Period:

03/2023-02/2026

Motivation

Electrons in the 5f and 6d orbitals are crucial to actinides’ physical and chemical behaviour and ultimately determines their properties. Few experimental methods can directly characterize the electronic structure. Among them, a prominent role is played by X-ray Absorption Near-Edge Structure (XANES) acquired in the High-Energy-Resolution Fluorescence Detected (HERFD) mode and Resonant Inelastic X-ray Scattering (RIXS). Through the excitation of a 2p and 3d electrons into the 6d and 5f states, the occupation, the electronic interactions and the degree of covalency experienced by these states can be probed. The complexity of the data analysis represents nowadays the main bottleneck to the extended use of these techniques to study actinides properties.

Objectives

The aim of this PhD thesis is to advance the fundamental understanding of the actinide systems through the use of these advanced X-ray techniques. This goal will be achieved by combining X-ray spectroscopy characterization with quantum chemical computational studies. Electronic structure calculations based on multiplet theory and density functional theory will be used to extract detailed information from the data. RIXS and HERFD calculations at the actinide M4,5 edges will be performed using the Quanty multiplet code, while the Finite Difference Method Near Edge Structure (FDMNES) code will be used for the study of the actinide L3-edge. State-of-the-art theoretical approaches applied to systematic investigation of model systems like actinides halides and oxides will be the playground to progress our understanding of 5f systems.

References

  1. Silva, C. L. et al. On the origin of low-valent uranium oxidation state. Nat. Commun. 15, 6861 (2024).
  2. Kvashnina, K. O. & Butorin, S. M. High-energy resolution X-ray spectroscopy at actinide M 4,5 and ligand K edges: what we know, what we want to know, and what we can know. Chem. Commun. 58, 327–342 (2022).
  3. Amidani, L. et al. Probing the Local Coordination of Hexavalent Uranium and the Splitting of 5f Orbitals Induced by Chemical Bonding. Inorg. Chem. 60, 16286–16293 (2021).
  4. Amidani, L. et al. Understanding the size effects on the electronic structure of ThO2 nanoparticles. Phys. Chem. Chem. Phys. 21, 10635–10643 (2019).
  5. Kvashnina, K. O., Butorin, S. M., Martin, P. & Glatzel, P. Chemical State of Complex Uranium Oxides. Phys. Rev. Lett. 111, 253002 (2013).