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| 2. |
- Gagliardi, L, et al.
(författare)
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A very short uranium-uranium bond: The predicted metastable U-2(2+)
- 2005
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 7:12, s. 2415-2417
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Tidskriftsartikel (refereegranskat)abstract
- Quantum chemical calculations, based on multiconfigurational wave functions and including relativistic effects, show that the U-2(2+) system has a large number of low-lying electronic states with S of 0 to 2 and Lambda ranging from zero to ten. These states share a very small bond length of about 2.30 angstrom, compared to 2.43 angstrom in neutral U-2. The Coulomb explosion to 2 U+ lowers the energy by only 1.6 eV and is separated by a broad barrier.
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| 3. |
- Gagliardi, L, et al.
(författare)
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Quantum chemical calculations show that the uranium molecule U-2 has a quintuple bond
- 2005
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 433:7028, s. 848-851
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Tidskriftsartikel (refereegranskat)abstract
- Covalent bonding is commonly described by Lewis's theory(1), with an electron pair shared between two atoms constituting one full bond. Beginning with the valence bond description(2) for the hydrogen molecule, quantum chemists have further explored the fundamental nature of the chemical bond for atoms throughout the periodic table, confirming that most molecules are indeed held together by one electron pair for each bond. But more complex binding may occur when large numbers of atomic orbitals can participate in bond formation. Such behaviour is common with transition metals. When involving heavy actinide elements, metal-metal bonds might prove particularly complicated. To date, evidence for actinide-actinide bonds is restricted to the matrix-isolation(3) of uranium hydrides, including H2U-UH2, and the gas-phase detection(4) and preliminary theoretical study(5) of the uranium molecule, U-2. Here we report quantum chemical calculations on U-2, showing that, although the strength of the U-2 bond is comparable to that of other multiple bonds between transition metals, the bonding pattern is unique. We find that the molecule contains three electron-pair bonds and four one-electron bonds (that is, 10 bonding electrons, corresponding to a quintuple bond), and two ferromagnetically coupled electrons localized on one U atom each-so all known covalent bonding types are contributing.
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| 4. |
- Gagliardi, L, et al.
(författare)
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The electronic spectrum of the UO2 molecule
- 2005
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 127:1, s. 86-91
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Tidskriftsartikel (refereegranskat)abstract
- The electronic spectrum of the UO2 Molecule has been determined using multiconfigurational wave functions together with the inclusion spin-orbit coupling. The molecule has been found to have a (5fphi)(7s), (3)Phi(2u), ground state. The lowest state of gerade symmetry, H-3(4g), corresponding to the electronic configuration (5f)(2) was found 3330 cm(-1) above the ground state. The computed energy levels and oscillator strengths were used for the assignment of the experimental spectrum in the energy range 17000-19000 and 27000-32000 cm(-1).
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| 5. |
- Hagberg, Daniel, et al.
(författare)
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The coordination of uranyl in water: A combined quantum chemical and molecular simulation study
- 2005
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 127:41, s. 14250-14256
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Tidskriftsartikel (refereegranskat)abstract
- The coordination environment of uranyl in water has been studied using a combined quantum mechanical and molecular dynamics approach. Multiconfigurational wave function calculations have been performed to generate pair potentials between uranyl and water. The quantum chemically determined energies have been used to fit parameters in a polarizable force field with an added charge transfer term. Molecular dynamics simulations have been performed for the uranyl ion and up to 400 water molecules. The results show a uranyl ion with five water molecules coordinated in the equatorial plane. The U-O(H2O) distance is 2.40 angstrom, which is close to the experimental estimates. A second coordination shell starts at about 4.7 angstrom from the uranium atom. No hydrogen bonding is found between the uranyl oxygens and water. Exchange of waters between the first and second solvation shell is found to occur through a path intermediate between association and interchange. This is the first fully ab initio determination of the solvation of the uranyl ion in water.
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| 6. |
- Roos, Björn, et al.
(författare)
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Quantum chemistry predicts multiply bonded diuranium compounds to be stable
- 2006
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 45:2, s. 803-807
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Tidskriftsartikel (refereegranskat)abstract
- Results from quantum chemical calculations that predict the existence of a series of diuranium molecules are reported. Two diuranium chlorides, U2Cl6 and U2Cl82-, and three different carboxylates, U-2(OCHO)(4), U-2(OCHO)(6), and U-2(OCHO)(4)Cl-2 have been studied. All species have been found to be stable with a multiply bonded U-2 unit.
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