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1.
I. O. Utkin Yu. A. Teterin V. A. Terekhov M. V. Ryzhkov A. Yu. Teterin L. Vukvcevic 《Radiochemistry》2005,47(4):334-344
The fine structure of the X-ray photoelectron spectrum of low-energy electrons and O
4,5(U) X-ray emission spectrum of uranyl fluoride UO2F2 (at binding energies from 0 to 40 eV) was identified on the basis of the electronic structure calculations for the [(UO2)F6]4− cluster with D
6h
point symmetry, simulating the nearest surrounding of uranium in UO2F2, by the relativistic X
α discrete variation method. It was shown that the U5f electrons can directly participate in chemical bonding, and U6p electrons, in formation of not only inner valence but also outer valence molecular orbitals. The sequence of the inner valence molecular orbitals in the binding energy region from 12 to 40 eV was established, which is essential for development of a procedure for determining the uranium-ligand bond length in the axial direction and in the equatorial plane of the uranyl compounds, based on the characteristics of their X-ray photoelectron spectra.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 305-314.Original Russian Text Copyright © 2005 by Utkin, Yu. Teterin, Terekhov, Ryzhkov, A. Teterin, Vukvcevic. 相似文献
2.
N. V. Ryabkova A. A. Lumpov V. A. Mikhalev A. A. Murzin A. Yu. Shadrin 《Radiochemistry》2010,52(4):399-402
The kinetics of the UO2 dissolution in the N2O4-H2O system was studied. At 25°C, the process is kinetically controlled, whereas at 55°C the process occurs initially under kinetic
control (3 min) and then under diffusion-kinetic control. At 80°C, the process occurs exclusively under diffusion-kinetic
control. The apparent activation energy was estimated at ∼39 kJ mol−1. 相似文献
3.
Thermal deformations of Na6(UO2)2O(MoO4)4 were studied by high-temperature powder X-ray diffraction. The compound crystallizes in the triclinic system, space group Р\(\bar 1\), a = 7.636(7), b = 8.163(6), c = 8.746(4) Å, α = 72.32(9)°, β = 79.36(4)°, γ = 65.79(5)°, V = 472.74(4) Å3. It is stable in the temperature interval 20–700°С. The thermal expansion coefficients (TECs) are α11 = 25.5 × 10–6, α22 = 7.8 × 10–6, and α33 = 1.1 × 10–6 (°C)–1. The orientation of the TEC pattern relative to the crystallographic axes is a33^Z = 45°, a33^X = 122°, a22^Z = 59°, and a22^X = 66°. The anisotropy of the thermal expansion is due to specific features of the crystal structure of the compound. 相似文献
4.
Yu. A. Teterin K. I. Maslakov M. V. Ryzhkov O. A. Traparic L. Vukvcevic A. Yu. Teterin A. D. Panov 《Radiochemistry》2005,47(3):215-224
Fine structure of the X-ray photoelectron and conversion spectra of low-energy (0–40 eV) electrons of uranium dioxide UO2 was analyzed based on the electronic structure calculations for the UO
8
12−
cluster with O
h
symmetry, simulating the nearest surrounding of uranium in UO2, by the relativistic X
α discrete variation method. It was predicted theoretically and validated experimentally that, in UO2, the U5f electrons (∼1 U5f electron) can directly participate in chemical bonding: ∼2 U5f electrons weakly contributing to chemical bonding are localized at −1.9 eV; ∼1 U5f electron participating in chemical bonding is delocalized in the range of outer valence molecular orbital energies from −4 to −9 eV; and unfilled U5f states are localized mostly at low (from 0 to 5 eV above zero) energies. It was shown experimentally that the U6p electrons actively participate in formation of not only inner valence but also outer valence (0.6 U6p electron) molecular orbitals. The density of the U6p states in UO2 was estimated experimentally. The composition and sequence of the inner valence molecular orbitals at energies within 13–40 eV were also elucidated.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 193–202.Original Russian Text Copyright © 2005 by Yu. Teterin, Maslakov, Ryzhkov, Traparic, Vukcevic, A. Teterin, Panov. 相似文献
5.
L. B. Serezhkina E. V. Peresypkina A. V. Virovets E. S. Klynin V. N. Serezhkin 《Radiochemistry》2011,53(5):457-461
The complex [UO2(OH)(CO(NH2)2)3]2(ClO4)2 (I) was synthesized. A single crystal X-ray diffraction study showed that compound I crystallizes in the triclinic system with the unit cell parameters a = 7.1410(2), b = 10.1097(2), c = 11.0240(4) Å, α = 104.648(1)°, β = 103.088(1)°, γ = 108.549(1)°, space group \(P\bar 1\), Z = 1, R = 0.0193. The uranium-containing structural units of the crystals are binuclear groups [UO2(OH)· (CO(NH2)2)3] 2 2+ belonging to crystal-chemical group AM2M 3 1 [A = UO 2 2+ , M2 = OH?, M1 = CO(NH2)2] of uranyl complexes. The crystal-chemical analysis of nonvalent interactions using the method of molecular Voronoi-Dirichlet polyhedra was performed, and the IR spectra of crystals of I were analyzed. 相似文献
6.
Phase transitions and thermal deformations of - and -Cs2(UO2)2(MoO4)3 were studied by high-temperature X-ray diffraction analysis. In heating of -Cs2(UO2)2(MoO4)3 to 625 ± 25°C, the reconstructive phase transition proceeds. -Cs2(UO2)2(MoO4)3 is stable up to 700 ±25°C. The thermal expansion of both phases is sharply anisotropic: 11 = 10 × 10–6, 22 = 33 × 10–6, 33 = 10 × 10–6, V = 53 × 10–6 deg–1 for -Cs(UO2)2(MoO4)3 and 11 = 13 × 10–6, 33 = 3 × 10–6, V = 31 × 10–6 deg–1 for -Cs2 (UO2)2 (MoO4)3. The anisotropy of thermal expansion is explained by features of the crystal structure of the compounds.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 405–407.Original Russian Text Copyright © 2004 by Nazarchuk, Krivovichev, Filatov. 相似文献
7.
The crystal structure of a previously unknown compound [CH3NH3][(UO2)(H2AsO4)3] was solved by direct methods and refined to R 1 = 0.038 for 3041 reflections with |F hkl | >-4σ |F hkl |. The compound crystallizes in the monoclinic system, space group P21/c, a = 8.980(1), b = 21.767(2), c = 7.867(1) Å, β = 115.919(5)°, V = 1383.1(3) Å3, Z = 4. In the structure of the compound, pentagonal bipyramids of uranyl ions, sharing bridging atoms with tetrahedral [H2AsO4]? anions, form strongly corrugated layered complexes [(UO2)(H2AsO4)3]? arranged parallel to the (100) plane. The protonated methylamine molecules [CH3NH3]+ form unidimensional tapelike packings parallel to the c axis and linked by hydrophilic-hydro-phobic interactions. The topology of the layered uranyl arsenate complex [(UO2)(H2AsO4)3]? is unusual for uranyl compounds and was not observed previously. A specific feature of this topology is the presence of monodentate arsenate “branches” arranged within the layer. 相似文献
8.
S. V. Krivovichev V. V. Gurzhiy P. C. Burns I. G. Tananaev B. F. Myasoedov 《Radiochemistry》2010,52(1):7-11
The compound [NH3(CH2)9NH3]2[(UO2)3(SeO4)5(H2O)2](H2O)x (1) was prepared by isothermal evaporation from aqueous uranyl selenate solutions containing 1,9-diaminononane. A structural study showed that the compound is a partially ordered organic-inorganic nanocomposite. The structural model of the inorganic complex was determined by single crystal X-ray diffraction a = 19.5572(5), c = 47.878(2) Å, V= 15859.1(9) Å3, Z= 12; R1 = 0.1318, wR2 = 0.3186 for 2808 reflections with |Fo| ≥ 4σF). The structure consists of double hydrogen-bonded [(UO2)3(SeO4)5(H2O)2]2- layers parallel to the (001) plane. The disordered protonated 1,9-diaminononane molecules and water molecules are arranged between the layers. The inorganic layered complex [(UO2)3(SeO4)5(H2O)2]2- belongs to a new type that was not observed previously in the structures of inorganic and organometallic compounds. 相似文献
9.
Thermodynamic models of a UO2-based melt and cubic solid solution were developed on the basis of the most accurate measurements of the UO2-Gd2O3 liquidus in a range of 0–30 mol. % of Gd2O3. These models enabled computing the phase diagram of this system in a temperature range of 1900–3200 K for all composition
varieties. 相似文献
10.
S. V. Krivovichev 《Radiochemistry》2008,50(5):450-454
The crystal structure of a previously unknown compound KNa3[(UO2)5O6(SO4)] [space group Pbca, a = 13.2855(15), b = 13.7258(18), c = 19.712(2) Å, V = 3594.6(7) Å3] was solved by direct methods and refined to R 1 = 0.055 for 3022 reflections with |F hkl | ≥ 4σ |F hkl |. In the structure there are five sym-metrically nonequivalent uranyl cations. They are linked by cationcation (CC) interactions to form a pentamer whose central cation is U(2)O 2 2+ forming two three-centered CC bonds. All the uranyl ions are coordinated in the equatorial plane by five O atoms, which leads to the formation of pentagonal bipyramids sharing common edges to form layers parallel to the (100) plane. The sulfate tetrahedron links the uranyl layers into a 3D framework. The K+ and Na+ cations are arranged in framework voids. A brief review of CC interactions in U(VI) compounds is presented. 相似文献
11.
G. V. Sidorenko M. S. Grigor’ev V. V. Gurzhiy D. N. Suglobov I. G. Tananaev 《Radiochemistry》2009,51(4):345-349
The crystal and molecular structure of uranyl acetylacetonate dimer was determined by single crystal X-ray diffraction. The compound crystallizes in the tetragonal system, a = 7.9420(2), c = 40.1240(13) Å (at 100 K), Z = 4, space group P41212. Dimeric uranyl acetylacetonate molecules in the crystal are formed by bridging bonding of one of O atoms of the acetylacetonate ligands with U atoms, so that the coordination polyhedra of U atoms (distorted pentagonal bipyramids) share a common equatorial edge. The dimer has a nonplanar structure, being significantly bent along the conventional line connecting the bridging O atoms. 相似文献
12.
V. V. Smolenskii A. L. Bove N. P. Borodina A. V. Bychkov A. G. Osipenko 《Radiochemistry》2004,46(6):583-586
A study was made of interaction between AlCl3 and room-temperature ionic liquid (RTIL) [C8H15N2][N(SO2CF3)2], or BuEtIm-Tf2N, and of anodic dissolution in RTIL of UO2 and of a simulated oxide fuel at 297–302 K, depending on the AlCl3 concentration. It was shown that anodic dissolution of UO2 pellets and a UO2-Al mixture in RTIL yields soluble uranium species. Potentiostatic electrolysis of the resulting solutions can yield uranium compounds at the cathode, though with low current efficiencies. The role of AlCl3 in these processes was suggested. A heterophase reaction between UO2 and AlCl3 was studied, depending on the content of AlCl3 in solution. It was found that the exchange reaction products, soluble uranium species, are accumulated in solution only at the molar ratio AlCl3/Tf2N > 1.Translated from Radiokhimiya, Vol. 46, No. 6, 2004, pp. 536–539.Original Russian Text Copyright © 2004 by Smolenskii, Bove, Borodina, Bychkov, Osipenko. 相似文献
13.
Cu2{(UO2)3[(S,Cr)O4]5}(H2O)17 crystals were prepared by evaporation of aqueous solutions. The crystal structure was solved by the direct method and refined to R
1 = 0.064 (wR
2 = 0.177) for 8120 reflections with ¦F
hkl¦ 4 ¦F
hkl¦. Rhombic system, space group Pbca, a = 18.0586(8), b = 19.9898(9), c = 20.5553(8) Å, V = 7420.2(6) Å3. The structure is based on {(UO2)3[(S,Cr)O4]5}4– anionic layers, formed by combination of UO7 pentagonal bipyramids and TO4 tetrahedra through common vertices. The { (UO2)3 [(S,Cr)O4]5}4– layers are parallel to the (010) plane. The Cu2+ (H2O)6 octahedra and additional water molecules are located in the interplanar space and provide binding of the layers in the structure by hydrogen bonds. Based on the occupancy of tetrahedral positions, more accurate chemical formula of the compound should be written as Cu2{(UO2)3[(S0.804 Cr0.196)O4]5} (H2O)17.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 408–411.Original Russian Text Copyright © 2004 by Krivovichev, Burns. 相似文献
14.
P. P. Puga K. P. Popovych P. S. Danilyuk V. N. Krasylynec G. D. Puga I. I. Turok V. A. Kel’man I. I. Chichura 《Inorganic Materials》2012,48(10):1033-1038
This paper examines the effect of doping level on the X-ray luminescence of TbO2-doped polycrystalline lithium tetraborate. It is shown that, when interpreting such spectra, it is convenient to proceed from the terms of free activator and constituent ions. We demonstrate that the emission lines of Tb3+ in doped polycrystalline lithium tetraborate are effectively excited in the band between 350 and 650 nm, which is predominantly due to electron transitions from the 5 D 3 and 5 D 4 excited states to spin-orbital levels of the 7 F J ground multiplet. The emission lines of lithium and boron in single-crystal and polycrystalline undoped lithium tetraborate are effectively excited in the band between 274 and 550 nm. 相似文献
15.
The compound (NH4)3[UO2(CH3COO)3]2(NCS) (I) was synthesized and examined by single crystal X-ray diffraction analysis. The compound crystallizes in the rhombic system with the unit cell parameters a = 11.5546(4), b = 18.5548(7), c = 6.7222(3) Å, V = 1441.19(10) Å3, space group P21212, Z = 2, R = 0.0345. The uranium-containing structural units of crystals of I are isolated mononuclear groups [UO2(CH3COO)3]? belonging to crystal-chemical group AB 3 01 (A = UO 2 2+ , B01 = CH3COO?) of uranyl complexes. The specific features of packing of the uranium-containing complexes in the crystal structure are considered. 相似文献
16.
W. Benosmane W. Benstaali A. Abbad Y. Benmalem H. A. Bentounes 《Journal of Superconductivity and Novel Magnetism》2018,31(10):3085-3090
In the present work, a self-consistent ab initio calculation using the full-potential linearized augmented plane wave (FP-LAPW) method within the framework of the spin-polarized density functional theory (DFT) was used to study the structural, electronic, and thermodynamic properties of Ca2CoNbO6 double perovskite compound. The generalized gradient approximation (GGA) described by Perdew–Burke–Ernzerhof (PBE) and GGA + U were used. The results obtained for the electronic properties show a ferrimagnetic and half-metallic behavior of the compound. The novelty of our work is the study of the thermodynamic properties of Ca2CoNbO6 double perovskite such as heat capacity and Debye temperature which showed an important effect of pressure compared to the temperature. 相似文献
17.
Thomas Jarlborg Antonio Bianconi 《Journal of Superconductivity and Novel Magnetism》2016,29(3):615-621
The electronic structures of La2NiO4+δ , where additional interstitial oxygens are forming stripes along (1,1,0), are presented. Spin-polarized calculations show that ferromagnetism on Ni sites is reduced near the stripes and enhanced far from the stripes. Totally, the magnetic moment becomes reduced because of interstitial oxygens. It is suggested that the oxygen interstitial concentration in oxygen-rich domains in nickelates suppress magnetism and give multiband metallic domains. 相似文献
18.
Multilayered oxide heteroepitaxial systems, including that of a 1-nm-thick Y2O3-stabilised ZrO2 (YSZ) sandwiched between layers of SrTiO3 (STO) [1], have been a subject of much interest lately due to their significantly enhanced ionic conductivities as compared to the
bulk materials. We aim to provide the foundation for understanding this increase in conductivity by considering the atomic
configurations at the interfaces of such systems, specifically a ZrO2/STO multilayer system. Possible stable lattice structures of pure ZrO2 in the system are explored using a genetic algorithm in which the interatomic interactions are modelled by simple pair potentials.
The energies of several of the more stable of these structures are then evaluated more accurately within density functional
theory (DFT). We find that the fluorite ZrO2 phase is unstable as a coherently strained epitaxial layer in the multilayer system. Instead, anatase-, columbite-, rutile-,
and pyrite-like ZrO2 epitaxies are found to be more stable, with the anatase-like epitaxy being the most stable structure over a wide range of
chemical potential of the components. We also find a high energy metastable structure resembling the tetragonal fluorite structure
which is predicted by DFT to be stabilised by SrO-terminated STO but not by TiO2-terminated STO. 相似文献
19.
Uranyl phosphate (UO2)3(PO4)2·8H2O was synthezied. Its dehydration was studied by X-ray diffraction, IR spectroscopy, and thermal and chemical analysis. The
dehydration products were isolated and characterized by X-ray diffraction and IR spectroscopy. Their structural features were
determined. 相似文献
20.
I. A. Charushnikova N. N. Krot Z. A. Starikova F. M. Dolgushin I. N. Polyakova 《Radiochemistry》2008,50(1):34-37
KNpO2(OOCH)2 was isolated from neutral Np(V) solutions with a high concentration of potassium formate. The crystal structure of this compound was determined. The structure consists of infinite anionic chains [NpO2(OOCH)2] n n? . Potassium cations are located between these chains. The Np coordination polyhedron is a hexagonal bipyramid whose equatorial plane is formed by the oxygen atoms of four HCOO? ions. The Np bipyramids in the chains are bound via common equatorial edges. The anionic chains in the structures of KNpO2(OOCH)2 and NH4NpO2(OOCH)2 studied previously have similar composition but different structure. 相似文献