Crystal Structure and Magnetic Properties of Uranium Hydride UH<sub>2</sub> Stabilized as a Thin Film

Havela, L.; Paukov, M.; Dopita, Milan; Horák, Lukáš; Drozdenko, Daria; Diviš, M.; Turek, I.; Legut, Dominik; Kývala, Lukáš; Gouder, T.; Seibert, Α.; Huber, F.

doi:10.1021/acs.inorgchem.8b02499

Cited by 15 publications

(5 citation statements)

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“…One cannot arbitrarily assign U 2+ in UTe; on the contrary, U 3+ is assigned, consistent with the available knowledge of bonding behaviors in U solids. In fact, U 2+ -containing solids could be prepared only under some extreme chemical or physical conditions. ,, The calculation results show that the occupation numbers of U 6d orbitals in UTe are smaller than 0.1, indicative of unoccupied states; consequently, its nominal composition can be written as U 3+ [e – ]Te 2– , suggesting the existence of itinerant conducting electron. Likewise, the nominal compositions of monovalent U 3 Te 4 and U 3 Te 5 could be expressed as [U 3+ ] 3 [e – ][Te 2– ] 4 and [U 3+ ] 3 [Te 2– ] 5 [h + ] (h + denotes positively charged hole), respectively, which is partially evidenced by the nearly identical U and Te ions from structure and charge analysis.…”

Section: Resultssupporting

confidence: 55%

“…In fact, U 2+ - containing solids could be prepared only under some extreme chemical or physical conditions. 16,17,51 The calculation results show that the occupation numbers of U 6d orbitals in UTe are smaller than 0. The evolution of U OS qm in binary tellurides can be viewed as the associated consequence of relatively weak coordinating albeit strong clustering abilities of Te.…”

Section: Resultsmentioning

confidence: 96%

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Theoretical Assignment of Oxidation State of Uranium in Binary, Ternary, and Quaternary Tellurides

et al. 2020

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The recent breakthrough in the discovery of nearly ferromagnetic spin-triplet superconductivity UTe2 has attracted vivid investigations regarding its physical properties; however, the fundamental-chemistry understanding of UTe2 and other U tellurides remains lacking. Hereby, a systematic first-principles calculation is conducted on the behavior of U binary, ternary, and quaternary tellurides, with particular focus on the rigorous assignment of quantum-mechanical oxidation state (OSqm) of U ions by counting the 5f orbital occupation number. The results show the trend and variation of U OSqm and disclose the correlation among OSqm, structure, and composition. Interestingly, OSqm behavior in tellurides is rather dissimilar from that in oxides, which is mainly due to the relatively weak U–Te bonding interaction and strong tendency of forming Te clusters or chains in solids. Among the considered tellurides, the highest OSqm of U ions is U4+ instead of the formally highest valent U6+ in the ionic limitation; the only exception occurs on molecular crystal U(TeOF5)6 in which U adopts U6+ because of the absence of U–Te bonds and the saturation of dominating U–O bonds.

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Section: Resultssupporting

confidence: 55%

Section: Resultsmentioning

confidence: 96%

Theoretical Assignment of Oxidation State of Uranium in Binary, Ternary, and Quaternary Tellurides

et al. 2020

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“…The three 6d and 7s electrons are characteristic of the itinerant nature associated with bonding behaviors, which is evidenced by the fact that the lowest oxidation state (OS) of U in almost all solid-state compounds under normal conditions is U 3+ . It should be emphasized that U 2+ can be achieved by judiciously tailoring the ligands or under some extreme conditions, − which is beyond the scope of the present discussion. Knowledge from U-based materials indicates that 5f 3 electrons play the decisive role in structure and bonding mainly because of the directionality and the environmentally sensitive localization-delocalization transition of f electrons.…”

Section: Introductionmentioning

confidence: 95%

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

2019

J. Phys. Chem. C

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Uranium (U) has attracted considerable fundamental and applied studies; among them, the rigorous determination of its chemical state is one of the crucial topics owing to its well-known multivalent feature associated with complicated chemical bonding. However, the related studies on solid-state U ternary or beyond ternary compounds are quite in lack. Herein, first-principles DFT + U calculations are performed to unambiguously determine the actual oxidation states of metal ions in U ternary oxides containing multivalent transition-metals (TMs: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W). For the first time, the actual oxidation states of U and TM in the ternary oxides are obtained in a quantitative and atom-resolved manner, thereby providing their nominal compositions. The results disclose the variations of U oxidation states with TM's properties, chemical surrounding, local structure, and oxygen vacancy. In terms of charge transfer, electronic structure, orbital energy level, and oxygen vacancy effect, I conclude that the oxidation state is the competitive consequence of those electronic and structural factors and that electron-structure-related factors play more important roles. Because of the increasing orbital expansion from 3d to 4d and 5d TMs, the latter TMs (Nb, Mo, W) have the greater tendency to form high oxidation states and suppress the formation of high oxidation states of U. On the contrary, 3d TMs, especially Cr, Mn, Fe, and Ni, tend to adopt low oxidation states, thereby promoting the emergence of high oxidation states of U.

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“…The high stability of UH 3 is most likely the reason why no UH 2 phase with the CaF 2 structure type (U sublattice forming the fcc structure), known to form for all 4f and most of 5f elements, appears in the equilibrium U-H phase diagram [14]. This phase was synthesized only in a thin-film form by reactive sputter deposition, which generally helps to avoid constraints of thermodynamic equilibrium [15]. UH 2 is also ferromagnetic, with T C ≈ 120 K being somewhat lower compared to both UH 3 phases.…”

Section: Uranium Hydrides In a Historical Perspective-structure And M...mentioning

confidence: 99%

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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Crystal Structure and Magnetic Properties of Uranium Hydride UH₂ Stabilized as a Thin Film

Cited by 15 publications

References 24 publications

Theoretical Assignment of Oxidation State of Uranium in Binary, Ternary, and Quaternary Tellurides

Theoretical Assignment of Oxidation State of Uranium in Binary, Ternary, and Quaternary Tellurides

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

Hydrogen in actinides: electronic and lattice properties

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Crystal Structure and Magnetic Properties of Uranium Hydride UH2 Stabilized as a Thin Film

Cited by 15 publications

References 24 publications

Theoretical Assignment of Oxidation State of Uranium in Binary, Ternary, and Quaternary Tellurides

Theoretical Assignment of Oxidation State of Uranium in Binary, Ternary, and Quaternary Tellurides

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

Hydrogen in actinides: electronic and lattice properties

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Crystal Structure and Magnetic Properties of Uranium Hydride UH₂ Stabilized as a Thin Film