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  • 1
    Electronic Resource
    Electronic Resource
    Lanthanide and Actinide Contractions: Relativistic and Shell Structure Effects (1995)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 6597-6598 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00129a026
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  • 2
    Electronic Resource
    Electronic Resource
    An ab initio study of the ionization potentials and f–f spectroscopy of europium atoms and ions (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 5481-5493 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The first three ionization potentials of europium and the f–f spectroscopy of the two lowest multiplets of Eu+3 have been calculated using ab initio spin–orbit configuration interaction techniques. To accomplish this, a new averaged relativistic effective core potential has been developed which leaves only the 5s, 5p, and 4f in the valence space. A series of configuration interaction calculations were carried out up through single and partial double excitations with a double-zeta quality basis set. The computed ionization values have an absolute error of about 0.1 eV from the experimental values. The computed f–f spectroscopy for the lowest 7F multiplet of Eu+3 has a RMS error with experiment of about 100 cm−1. The computed f–f spectroscopy for the first excited 5D multiplet has a higher RMS error of about 350 cm−1. The computed center of gravity separation between the 5D–7F multiplet is underestimated by 750 cm−1. Comparisons between non-spin–orbit and spin–orbit configuration interaction calculations for the separations of the centers of gravity of multiplets are very favorable up through single and double excitations with differences of a tenth of an eV or less. The spin–orbit configuration interaction calculations are among the largest ever performed for lanthanides, with expansion lengths in excess of 1.9 million double-group-adapted functions. The calculations were achieved by application of a new parallel spin–orbit configuration interaction component in the COLUMBUS Program System. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1455619
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  • 3
    Electronic Resource
    Electronic Resource
    The chemistry of superheavy elements. III. Theoretical studies on element 113 compounds (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 6422-6433 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The chemistry of element 113 is investigated by theoretical methods. The results of fully relativistic calculations for (113)H and (113)F are compared with those derived by other techniques to obtain an indication of the accuracy of the more approximate models as well as the importance of including scalar and/or spin–orbit relativistic effects. Both of these effects are found to be important. The spin–orbit coupled pseudopotential approximation yields results of satisfactory accuracy, but the two relativistic methods that do not include spin–orbit coupling (Douglas–Kroll and scalar relativistic pseudopotential method) do not agree so well with each other. The calculated properties of (113)H and (113)F and a number of other hydrides and halides of element 113 are compared with the properties of the equivalent compounds of the lighter group 13 elements. In general, element 13 exhibits behavior that is consistent with its placement in group 13 of the periodic table. Some of its properties are found to be somewhat unusual however, e.g., the element is relatively electronegative, the molecules (113)H3, (113)F3, and (113)Cl3 are predicted to be T-shaped rather than trigonal planar, and the 6d electrons of element 113 participate to a significant extent in chemical bonding. Compounds where element 113 is present in the +5 oxidation state are considered as well but are predicted to be thermodynamically unstable. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480168
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  • 4
    Electronic Resource
    Electronic Resource
    A point-charge model for the nuclear quadrupole moment: Coupled-cluster, Dirac–Fock, Douglas–Kroll, and nonrelativistic Hartree–Fock calculations for the Cu and F electric field gradients in CuF (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 6722-6738 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A point charge model for the nuclear quadrupole moment tensor (PCNQM) is developed in order to determine accurate electric field gradients (EFG) at the relativistic and correlated levels. The symmetric s contributions arising from the Poisson equation are avoided by using an appropriate point charge distribution in three-dimensional space. It is shown that the PCNQM model yields virtually the same EFGs compared to the conventional method of expectation values, if the point charges are set at small displacements from the nucleus (d〈10−13 m) and the SCF energy is converged out to 12 significant figures. We further demonstrate that the choice of the point charge ζ is not very critical to the PCNQM perturbation, and that the correlation energy at both the nonrelativistic and relativistic level of theory depends linearly on ζ. This suggests that accurate EFG tensors can be obtained by performing only two correlated calculations for each atom and tensor component. The PCNQM model is tested on one-electron atoms and on the Cu and F EFG in CuF. Relativistic and correlation effects on EFGs are discussed in detail. A Z-expansion on one-electron systems demonstrates that the relativistic correction scales ∼Z5. For the CuF molecule Douglas–Kroll and Dirac–Fock coupled cluster calculations are in good agreement with each other. At the best level of theory (coupled cluster Dirac–Fock plus correction from basis set incompleteness) we obtain a nuclear quadrupole coupling constant for 63Cu of 23 Mhz. This is in very good agreement with the experimental result of 22 MHz considering the large standard deviation of the 63Cu nuclear quadrupole moment applied, 220(10) mb. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476088
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  • 5
    Electronic Resource
    Electronic Resource
    Experimental and theoretical determination of the magnetic dipole transition moment for the Br(4p5)(2P1/2←2P3/2) fine-structure transition and the quantum yield of Br(2P1/2) from the 193 nm photolysis of BrCN (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7821-7831 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The integrated-absorption coefficients of several hyperfine lines of the magnetic dipole allowed transition of the bromine atom, Br, center at 3685.2 cm−1 were measured, and a value for the square of the magnetic dipole transition moment of the Br atom was determined. A theoretical calculation for the magnetic dipole transition moment was also carried out using a relativistic ab initio atomic structure formulation. The theoretical value was in excellent agreement with the value predicted assuming pure LS coupling, and in reasonable agreement with experiment. The Br atom was generated in equal concentration with the cyano radical (CN) by the 193 nm photolysis of cyanogen bromine, BrCN. The CN radicals were titrated by the rapid reaction with C3H8 to generate HCN and a small amount of HNC. Both time-resolved and frequency-scanned infrared absorption spectroscopy were used to monitor the Br, HCN, and HNC species. The photolysis of BrCN at 193 nm produced both the ground state Br(2P3/2) and the spin-orbit excited Br(2P1/2) atoms, and the yield for the production of Br(2P1/2) atoms was measured to be 0.31±0.01. The rate constants for the quenching of Br(2P1/2) by BrCN and C3H8 at 293 K were also determined. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478689
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  • 6
    Electronic Resource
    Electronic Resource
    The chemistry of the superheavy elements. I. Pseudopotentials for 111 and 112 and relativistic coupled cluster calculations for (112)H+, (112)F2, and (112)F4 (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 3623-3632 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: One- and two-component (spin–orbit coupled) relativistic and nonrelativistic energy adjusted pseudopotentials and basis sets for the elements 111 and 112 are presented. Calculations on the positively charged monohydride of the recently discovered superheavy element 112 are reported. Electron correlation is treated at the multireference configuration interaction and coupled cluster level and fine structure effects are derived from a single-reference configuration interaction treatment. Relativistic effects decrease the (112)H+ bond distance by 0.41 Å. This bond contraction is similar to the one calculated recently for (111)H [Chem. Phys. Lett. 250, 461 (1996)]. As a result the bond distance of (112)H+ (1.52 Å) is predicted to be smaller compared to those of the hydrides of the lighter congeners HgH+ (1.59 Å), CdH+ (1.60 Å) and similar to that of ZnH+ (1.52 Å). We predict that (112)H+ is the most stable hydride in the Group 12 series due to relativistic effects. As in the case of (111)H the relativistic increase of the stretching force constant is quite large, from 1.5 to 4.3 mdyn/Å at the coupled cluster level. The trend in the dipole polarizabilities of the Group 12 elements is discussed. Relativistic and electron correlation effects are nonadditive and due to the relativistic ns contraction (n=7 for 112), correlation effects out of the (n−1)d core are more important at the relativistic than the nonrelativistic level. We also show evidence that element 112 behaves like a typical transition element, and as a consequence the high oxida-tion state +4 in element 112 might be accessible. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473437
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  • 7
    Electronic Resource
    Electronic Resource
    The chemistry of the superheavy elements. II. The stability of high oxidation states in group 11 elements: Relativistic coupled cluster calculations for the di-, tetra- and hexafluoro metallates of Cu, Ag, Au, and element 111 (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 3935-3943 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The stability of the high oxidation states +3 and +5 in Group 11 fluorides is studied by relativistic Møller–Plesset (MP) and coupled cluster methods. Higher metal oxidation states are stabilized by relativistic effects. As a result, the hexafluoro complex of the Group 11 element with nuclear charge 111 and oxidation state +5 is the most stable compared to the other congeners. The results also suggest that AgF6− is thermodynamically stable and, therefore, it might be feasable to synthesize this compound. For the copper fluorides we observe very large oscillations in the Møller–Plesset series up to the fourth order. Nonrelativistic calculations lead to the expected trend in the metal–fluorine bond distances for the MF2− compounds, CuF2−〈AgF2−〈AuF2−〈(111)F2−. However, relativistic effects change this trend to CuF2−〈AuF2−〈(111)F2−〈AgF2−. Vibrational frequencies are predicted for all compounds. Where experimental data are available, they generally agree very well with our calculated results. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476993
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  • 8
    Electronic Resource
    Electronic Resource
    Relativistic effects in nuclear quadrupole coupling (1997)
    Springer
    Theoretical chemistry accounts 96 (1997), S. 92-104 
    Details
    ISSN: 1432-2234
    Keywords: Key Words: Relativistic corrections ; Nuclear quadrupole coupling ; Electric field gradients ; Spin-orbit coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. Relativistic effects strongly influence the nuclear quadrupole coupling of atoms, molecules or solids. As first shown by Casimir in 1936, in the atomic or single-centre case, for the two states j=l±s, three radial electric-field-gradient (EFG) integrals, R ++,R +−, and R, must be introduced. The relativistic correction factors, defined for operator as have quite different values for the three combinations. For example, for the Bi atom ground state 6p shell at Dirac-Fock(DF) level, C ++ and C +− are 1.28 and 1.91, respectively, while q −,− vanishes entirely, due to j=1/2. There also is a dependence on the n quantum number. In addition to these relativistic changes of the integrals (at the atomic centre), spin-orbit tilting effects may occur, even at light atoms, bonded to heavy ones. We have produced DF-level, EFG integrals for the elements 1–93, investigated the hydrogen-like, n-dependent correction factors, C and used simple molecular-orbital models for estimating the spin-orbit tilting effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002140050209
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  • 9
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    Relativistic coupled-cluster static dipole polarizabilities of the alkali metals from Li to element 119 (1999)
    American Physical Society
    Details
    Publication Date: 1999-10-01
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Physical Society
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  • 10
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    A Density Functional Embedded Cluster Study of Proposed Active Sites in Heterogeneous Ziegler−Natta Catalysts (2002)
    American Chemical Society
    Details
    Publication Date: 2002-09-01
    Print ISSN: 0024-9297
    Electronic ISSN: 1520-5835
    Topics: Chemistry and Pharmacology , Physics
    Published by American Chemical Society
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