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Theoretical insight into the magnetic circular dichroism of uranium N 6,7 ‐edge X‐ray absorption
Author(s) -
Ramanantoanina Harry,
Gruden Maja
Publication year - 2020
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.26081
Subject(s) - magnetic circular dichroism , chemistry , ligand field theory , zeeman effect , electron , x ray magnetic circular dichroism , hamiltonian (control theory) , atomic physics , ground state , x ray absorption spectroscopy , electronic structure , absorption spectroscopy , unpaired electron , uranium , circular dichroism , ion , magnetic field , spectral line , physics , crystallography , computational chemistry , mathematical optimization , mathematics , organic chemistry , quantum mechanics , astronomy , nuclear physics
We use ligand‐field density functional theory to determine the electronic structure and to model magnetic circular dichroism in the X‐ray absorption spectroscopy (XAS) of uranium compounds. This study extends earlier work on tetravalent uranium ion, in which a model Hamiltonian was set up in order to study electronic structure with three nonequivalent 4 f , 5 f , and 6 d electrons. In the earlier work, the model Hamiltonian took into consideration the interelectron repulsion, spin‐orbit coupling interaction, and ligand‐field splitting. Uranium N 6,7 ‐edge XAS spectra were calculated on the basis of the 5 f 2 → 4 f 13 5 f 2 6 d 1 electron transition, showing spectral profiles that were mainly dominated by 4 f electron spin‐orbit coupling, as well as 6 d ligand‐field splitting. Fine structures were also observed due to the interelectronic repulsion between 4 f ‐5 f , 4 f ‐6 d , and 5 f ‐6 d electrons. Here, the theoretical study is extended to take into consideration the presence of an external magnetic field, incorporating into the model Hamiltonian for three‐open‐shell electron configuration a term for Zeeman interaction. Therefore, we are able to model spectra with a left‐circularly and right‐circularly polarized X‐ray, demonstrating evidence of X‐ray magnetic circular dichroism (XMCD) for a tetravalent U 4+ ion in the molecular (U( η 8 ‐C 8 H 8 ) 2 ) complex. The XMCD originates from a ground‐state electronic structure with open‐shell 5 f electrons. Furthermore, the present calculation of uranium N 6,7 ‐edge XAS and XMCD spectra also enables the ligand‐field bonding analysis of the coordination compound.