XPS, UPS, and BIS study of pure and alloyed β-UH3 films: Electronic structure, bonding, and magnetism

Havela, L.; Paukov, M.; Dopita, Milan; Horák, Lukáš; Cieslar, Miroslav; Drozdenko, Daria; Minárik, Peter; Turek, I.; Diviš, M.; Legut, Dominik; Kývala, Lukáš; Gouder, T.; Huber, F.; Seibert, Α.; Tereshina-Chitrova, E. A.

doi:10.1016/j.elspec.2019.146904

Cited by 9 publications

(12 citation statements)

References 33 publications

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“…One should notice the shift of 6p 3/2 line towards higher binding energies in the hydride. This behavior is also in line with theory predictions [73]. Figure 10 also demonstrates that a partial oxidation leads to the development of the emission at 2 eV and to a reduction of intensity close to E F .…”

Section: Electron Spectroscopiessupporting

confidence: 89%

“…The more shallow 5d states react to hydrogenation by a slightly larger shift of 0.5 eV, as shown by the U-5d spectra. The small energy shifts can be qualitatively understood by the fact that the polar bonding does not affect significantly the 5f states, which are more localized in the core than the 6d and 7s states, impacting mainly the more extended 6p states [73].…”

Section: Electron Spectroscopiesmentioning

confidence: 99%

“…On the other hand, LDA underestimates the lattice parameter and therefore it needs to be combined with a larger U [72]. The valence-band spectroscopy can discriminate between these two cases: the positions of the occupied and unoccupied 5f states in UH 3 are very close to the positions of the 5f states in uranium metal [73]. Since the uranium metal is very well described by DFT without any Hubbard correction, the correction cannot be large in UH 3 either, which indicates that GGA + U with a rather small Coulomb U should be the best model for the electronic structure of UH 3 among the DFT + U family of methods.…”

Section: Computational Studies-toward a Comprehensive Model Of Uhmentioning

confidence: 99%

“…The computations reveal that such spectrum is actually reflecting not the ground state density of states (DOS), but the final-state 5f 2 multiplets, reached by emitting an electron from the 5f 3 ground state. Similarly, NpH 3 can be possibly interpreted as Comparison of XPS spectra of UH 3 and U-metal thin films [73] on the background of calculated densities of states using the FPLO fully relativistic method and the LDA functional (dotted lines). While the intensity close below the Fermi level can be attributed mainly to the 5f states, one can notice additional spectral density in the hydride, attributed mainly to hybridized 6d-1s states in the range 4-7 eV below E F .…”

Section: Electron Spectroscopiesmentioning

confidence: 99%

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Hydrogen in actinides: electronic and lattice properties

Havela

Legut

Kolorenč³

2023

Rep. Prog. Phys.

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Hydrides of actinides, their magnetic, electronic, transport, and thermodynamic properties are discussed within a general framework of H impact on bonding, characterized by volume expansion, affecting mainly the 5f states, and a charge transfer towards H, which influences mostly the 6d and 7s states. These general mechanisms have diverse impact on individual actinides, depending on the degree of localization of their 5f states. Hydrogenation of uranium yields UH2 and UH3, binary hydrides that are strongly magnetic due to a 5f band narrowing and reduction of the 5f‐6d hybridization. Pu hydrides become magnetic as well, mainly as a result of the stabilization of the magnetic 5f 5 state and elimination of the admixture of the non‐magnetic 5f 6 component. Ab‐initio computational analyses, which for example suggest that the ferromagnetism of β‐UH3 is rather intricate involving two non‐collinear sublattices, are corroborated by spectroscopic studies of sputter‐deposited thin films, yielding a clean surface and offering a variability of compositions. It is found that valence‐band photoelectron spectra cannot be compared directly with the 5f n ground‐state density of states. Being affected by electron correlations in the excited final states, they rather reflect the atomic (n‐1) multiplets. Similar tendencies can be identified also in hydrides of binary and ternary intermetallic compounds. H absorption can be used as a tool for fine tuning of electronic structure around a quantum critical point. A new direction is represented by actinide polyhydrides with a potential for high‐temperature superconductivity.

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Section: Electron Spectroscopiessupporting

confidence: 89%

Section: Electron Spectroscopiesmentioning

confidence: 99%

Section: Computational Studies-toward a Comprehensive Model Of Uhmentioning

confidence: 99%

Section: Electron Spectroscopiesmentioning

confidence: 99%

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Hydrogen in actinides: electronic and lattice properties

Havela

Legut

Kolorenč³

2023

Rep. Prog. Phys.

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“…It is worth mentioning that the O 2p 1/2 and O 2p 3/2 orbitals can hybridize with the U 6d and U 7s orbitals. ,, Admittedly, accurate deconvolution and assignment of broad O 2p peaks into O 2p 1/2 and O 2p 3/2 and their hybridization (with U 6d and U 7s) peak are almost impossible due to the lack of relevant references. Since this work focuses on U(IV) to U(VI) oxidation states and there are no U 6d and U 7s electrons in uranium at oxidation states IV–VI, we only deconvoluted the broad O 2p peak to O 2p 1/2 and O 2p 3/2 peaks without taking the peaks for hybridization orbitals into account.…”

Section: Resultsmentioning

confidence: 99%

Exploring the Change in Redox Reactivity of UO₂ Induced by Exposure to Oxidants in HCO₃^– Solution

Liu

Jönsson

2023

Inorg. Chem.

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Understanding the possible change in UO2 surface reactivity after exposure to oxidants is of key importance when assessing the impact of spent nuclear fuel dissolution on the safety of a repository for spent nuclear fuel. In this work, we have experimentally studied the change in UO2 reactivity after consecutive exposures to O2 or γ-radiation in aqueous solutions containing 10 mM HCO3 –. The experiments show that the reactivity of UO2 toward O2 decreases significantly with time in a single exposure. In consecutive exposures, the reactivity also decreases from exposure to exposure. In γ-radiation exposures, the system reaches a steady state and the rate of uranium dissolution becomes governed by the radiolytic production of oxidants. Changes in surface reactivity can therefore not be observed in the irradiated system. The potential surface modification responsible for the change in UO2 reactivity was studied by XPS and UPS after consecutive exposures to either O2, H2O2, or γ-radiation in 10 mM HCO3 – solution. The results show that the surfaces were significantly oxidized to a stoichiometric ratio of O/U of UO2.3 under all the three exposure conditions. XPS results also show that the surfaces were dominated by U(V) with no observed U(VI). The experiments also show that U(V) is slowly removed from the surface when exposed to anoxic aqueous solutions containing 10 mM HCO3 –. The UPS results show that the outer ultrathin layer of the surfaces most probably contains a significant amount of U(VI). U(VI) may form upon exposure to air during the rinsing process with water prior to XPS and UPS measurements.

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Electrons and phonons in uranium hydrides - effects of polar bonding

Kývala

Havela

Kądzielawa

et al. 2022

Journal of Nuclear Materials

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XPS, UPS, and BIS study of pure and alloyed β-UH3 films: Electronic structure, bonding, and magnetism

Cited by 9 publications

References 33 publications

Hydrogen in actinides: electronic and lattice properties

Hydrogen in actinides: electronic and lattice properties

Exploring the Change in Redox Reactivity of UO₂ Induced by Exposure to Oxidants in HCO₃^– Solution

Electrons and phonons in uranium hydrides - effects of polar bonding

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XPS, UPS, and BIS study of pure and alloyed β-UH3 films: Electronic structure, bonding, and magnetism

Cited by 9 publications

References 33 publications

Hydrogen in actinides: electronic and lattice properties

Hydrogen in actinides: electronic and lattice properties

Exploring the Change in Redox Reactivity of UO2 Induced by Exposure to Oxidants in HCO3– Solution

Electrons and phonons in uranium hydrides - effects of polar bonding

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Product

Resources

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Exploring the Change in Redox Reactivity of UO₂ Induced by Exposure to Oxidants in HCO₃^– Solution