Resonant emission of UO2, U3O8, and UO2+x valence electrons under SR excitation near the O4,5(U) absorption edge

Teterin, A. Yu.; Ryzhkov, M. V.; Teterin, Yu. A.; Maslakov, K. I.; Reich, T.; Молодцов, С. Л.

doi:10.1134/s0022476611020089

Cited by 4 publications

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“…The peak of the U 5f electrons weakly participating in the chemical bond in UO 2+ x is observed in the photoelectron and X-ray photoelectron − ,, spectra around 0 BE. Spectra of compounds containing U 6+ do not exhibit this peak .…”

Section: Introductionmentioning

confidence: 93%

“…The IVMO formation in uranium oxides due to interaction of the U 6p and O 2s atomic orbitals (AO) also results in formation of structure in other X-ray (emission, conversion, Auger) spectra of uranium oxides. ,− These structure parameters correlate with the uranium–oxygen interatomic distances in axial and equatorial directions in uranyl compounds and serve for quantitative determination of these compounds. , …”

Section: Introductionmentioning

confidence: 99%

“…59,67,68,69 This structure parameters correlate with the uranium-oxygen interatomic distances in axial and equatorial directions in uranyl compounds and serve for quantitative determination of these compounds. 50,59 The peak of the U 5f electrons weakly participating in chemical bond in UO 2+x is observed in the photoelectron 70 and X-ray photoelectron 52,53,54,68,69 spectra around zero BE.…”

Section: Introductionmentioning

confidence: 99%

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XPS Study of Ion Irradiated and Unirradiated UO₂ Thin Films

et al. 2016

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XPS determination of the oxygen coefficient k O =2+x and ionic (U 4+ , U 5+ and U 6+ ) composition of oxides UO 2+x formed on the surfaces of differently oriented (hkl) planes of thin UO 2 films on LSAT (Al 10 La 3 O 51 Sr 14 Ta 7 ) and YSZ (yttria-stabilized zirconia) substrates was performed. The U 4f and O 1s core-electron peak intensities as well as the U 5f relative intensity before and after the 129 Xe 23+ and 238 U 31+ irradiations were employed. It was found that the presence of uranium dioxide film in air results in formation of oxide UO 2+x on the surface with mean oxygen coefficients k O in the range 2.07-2.11 on LSAT and 2.17-2.23 on YSZ substrates. These oxygen coefficients depend on the substrate and weakly on the crystallographic orientation.On the basis of the spectral parameters it was established that uranium dioxide films AP2,3 on the LSAT substrates have the smallest k O values, and from the XRD and EBSD results it follows that these samples have a regular monocrystalline structure. The XRD and EBSD results indicate that samples AP5-7 on the YSZ substrates have monocrystalline structure, however, they have the highest k O values. The observed difference in the k O values, probably, caused by the different nature of the substrates: the YSZ substrates provide 6.4% compressive strain, whereas (001) LSAT substrates result only in 0.03% tensile strain in the UO 2 films.129 Xe 23+ irradiation (92 MeV, 4.8 × 10 15 ions/cm 2 ) of uranium dioxide films on the LSAT substrates was shown to destroy both long range ordering and uranium close environment, which results in increase of uranium oxidation state and regrouping of oxygen ions in uranium close environment. 238 U 31+ (110 MeV, 5 × 10 10 , 5 × 10 11 , 5 × 10 12 ions/cm 2 ) irradiations of uranium dioxide films on the YSZ substrates were shown to form the lattice damage only with partial destruction of the long range ordering.3

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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XPS Study of Ion Irradiated and Unirradiated UO₂ Thin Films

et al. 2016

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“…2 U 3 O 8 is also the most common form of uranium found in nature and so investigation of its fundamental properties is pertinent to a detailed understanding of nuclear fuel materials. 8,11,12 After UO 2 , U 3 O 8 is the most rigorously analysed uranium oxide, with many structural, 8,13-18 thermodynamic 2,4,[19][20][21][22][23] and electronic [24][25][26][27][28][29][30][31] experimental studies as well as a number of theoretical investigations. [10][11][12][32][33][34] αand β-U 3 O 8 have been widely acknowledged as having orthorhombic symmetry for many years, although a number of space groups have been proposed.…”

Section: Introductionmentioning

confidence: 99%

Density functional theory investigation of the layered uranium oxides U₃O₈ and U₂O₅

et al. 2015

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Oxidation of UO(2) in the nuclear fuel cycle leads to formation of the layered uranium oxides. Here we present DFT simulations of U(2)O(5) and U(3)O(8) using the PBE + U functional to examine their structural, electronic and mechanical properties. We build on previous simulation studies of Amm2 α-U(3)O(8), P2(1)/m β-U(3)O(8) and P6[combining macron]2m γ-U(3)O(8) by including C222 α-U(3)O(8), Cmcm β-U(3)O(8) and Pnma δ-U(2)O(5). All materials are predicted to be insulators with no preference for ferromagnetic or antiferromagnetic ordering. We predict δ-U(2)O(5) contains exclusively U(5+) ions in an even mixture of distorted octahedral and pentagonal bipyramidal coordination sites. In each U(3)O(8) polymorph modelled we predict U(5+) ions in pentagonal bipyramidal coordination and U(6+) in octahedral coordination, with no U(4+) present. The elastic constants of each phase have been calculated and the bulk modulus is found to be inversely proportional to the volume per uranium ion. Finally, a number of thermodynamic properties are estimated, showing general agreement with available experiments; for example α- and β-U(3)O(8) are predicted to be stable at low temperatures but β-U(3)O(8) and γ-U(3)O(8) dominate at high temperature and high pressure respectively.

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“…Studies of the valence electronic states in UO 2 employ photoelectron (PES) and X‐ray photoelectron spectroscopy (XPS) . Auger O KLL spectrum, O 4,5 (U)‐edge resonant emission spectra, nonresonant and resonant O 4,5 (U) emission spectra, valence electron conversion spectra (CES), X‐ray absorption spectra (XAS), and resonant inversion photoelectron spectra of UO 2 have been studied previously.…”

Section: Introductionmentioning

confidence: 99%

The nature of the chemical bond in UO₂

Maslakov

Teterin

Ryzhkov

et al. 2019

Int J of Quantum Chemistry

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The nature of the chemical bond in UO2 was analyzed taking into account the X‐ray photoelectron spectroscopy (XPS) structure parameters of the valence and core electrons, as well as the relativistic discrete variation electronic structure calculation results for this oxide. The ionic/covalent nature of the chemical bond was determined for the UO8 (D4h) cluster, reflecting uranium's close environment in UO2, and the U13O56 and U63O216 clusters, reflecting the bulk of solid uranium dioxide. The bar graph of the theoretical valence band (from 0 to ~35 eV) of XPS spectrum was built such that it was in satisfactory agreement with the experimental spectrum of a UO2 single crystalline thin film. It was shown that unlike the crystal field theory results, the covalence effects in UO2 are significant due to the strong overlap of the U 6p and U 5f atomic orbitals with the ligand orbitals, in addition to the U 6d atomic orbital (AO). A quantitative molecular orbital (MO) scheme for UO2 was built. The contribution of the MO electrons to the chemical bond covalence component was evaluated on the basis of the bond population values. It was found that the electrons of inner valence molecular orbitals (IVMO) weaken the chemical bond formed by the electrons of outer valence molecular orbitals (OVMO) by 32% in UO8 and by 25% in U63O216.

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Resonant emission of UO2, U3O8, and UO2+x valence electrons under SR excitation near the O4,5(U) absorption edge

Cited by 4 publications

References 9 publications

XPS Study of Ion Irradiated and Unirradiated UO₂ Thin Films

XPS Study of Ion Irradiated and Unirradiated UO₂ Thin Films

Density functional theory investigation of the layered uranium oxides U₃O₈ and U₂O₅

The nature of the chemical bond in UO₂

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Resonant emission of UO2, U3O8, and UO2+x valence electrons under SR excitation near the O4,5(U) absorption edge

Cited by 4 publications

References 9 publications

XPS Study of Ion Irradiated and Unirradiated UO2 Thin Films

XPS Study of Ion Irradiated and Unirradiated UO2 Thin Films

Density functional theory investigation of the layered uranium oxides U3O8 and U2O5

The nature of the chemical bond in UO2

Contact Info

Product

Resources

About

XPS Study of Ion Irradiated and Unirradiated UO₂ Thin Films

XPS Study of Ion Irradiated and Unirradiated UO₂ Thin Films

Density functional theory investigation of the layered uranium oxides U₃O₈ and U₂O₅

The nature of the chemical bond in UO₂