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  • 1
    Electronic Resource
    Electronic Resource
    Relativistic MCSCF by means of quasidegenerate direct perturbation theory. I. Theory (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 3540-3558 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Relativistic MC-SCF (multiconfiguration self-consistent field) in terms of quasidegenerate direct perturbation theory (DPT) of relativistic effects is formulated based on a recently presented theory of effective Hamiltonians for electrons in a model space. The appropriately defined diagonal and nondiagonal parts of operators play a key role in this context. Their definition is based on stationary conditions for the MC-SCF wave function. The formalism starts from nonrelativistic MC-SCF theory. The leading relativistic correction appears as an expectation value in terms of the nonrelativistic MC-SCF function, while the higher-order relativistic corrections require a coupled-MC-SCF type approach. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480509
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  • 2
    Electronic Resource
    Electronic Resource
    Relativistic MCSCF by means of quasidegenerate direct perturbation theory. II. Preliminary applications (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 3559-3571 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The relativistic multiconfiguration self-consistent field (MCSCF) theory by means of (quasidegenerate) direct perturbation theory (DPT) is formulated and implemented through the leading order. Systematic investigations of nondynamical correlation and relativistic effects in berylliumlike systems are carried out. For this sequence, it appears that the single-state first-order DPT is valid only for the nuclear charge up to 30 or so. Calculations for the spectroscopic constants of the molecules of homonuclear halogen dimers X2 (X=F, Cl, Br, I, At) and TlX (X=F, Cl, Br, I) are performed at all-electron SCF (self-consistent field) and complete active space SCF levels, with the aim to demonstrate the efficiency of DPT by comparing with other relativistic calculations. Spin–orbit coupling affects the energies of the open-shell atoms and is taken into account for the binding energies. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480510
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  • 3
    Electronic Resource
    Electronic Resource
    Spectroscopic constants of gold and eka-gold (element 111) diatomic compounds: The importance of spin–orbit coupling (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 3730-3735 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Scalar-relativistic density functional calculations in the zeroth-order regular approximation as well as fully relativistic Dirac–Kohn–Sham calculations have been performed to investigate spectroscopic constants of the eka-gold (element 111) compounds (111) X (X=H, F, Cl, Br, O, Au) and the dimer of element 111. For calibration, we also report results for homologous gold compounds. The bond lengths for the compounds of element 111 are similar but slightly larger than those of the gold compounds. Spin–orbit coupling increases the bond length by a few pm. For the hydride and the halides, the force constants of the eka-gold compounds are generally larger than those of the gold compounds although the dissociation energy is smaller. The oxide of eka-gold is more strongly bound than the gold oxide. The dimer of element 111 has an open shell instead of a closed-shell electronic structure and is less stable than the gold dimer. The effect of spin–orbit coupling on the dissociation energy depends on the extent to which spin–orbit coupling is quenched in the molecule. This effect has been estimated based on a spinor occupation population analysis. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478237
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  • 4
    Electronic Resource
    Electronic Resource
    Fully relativistic density functional calculations of the ground and excited states of Yb, YbH, YbF, and YbO (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 2886-2895 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Fully relativistic density functional calculations using the recently developed Beijing 4-component density functional program package (BDF) were performed for a large number of excited states of the ytterbium atom and the spectroscopic constants of the ground and some excited states of the diatomic molecules YbH, YbF and YbO. It is shown that in a relativistic framework based on the Dirac–Coulomb Hamiltonian modern (nonrelativistic) density functionals work fairly well even for the rather compact 4f shell, i.e., they quantitatively reproduce the excitation energies due to the occupation changes in the 4f shell, in contrast to previous statements made by other authors. The nondegeneracy induced by the approximate density functionals to the degenerate open 4f shell is found to be almost independent of the occupancy of outer shells as well as Hund's coupling and of the same order as that for the first transition metals. After subtracting the unphysical nondegeneracy we obtain reasonable patterns of excited states due to different occupations of the 4f spinors for the molecules studied here. Although the spectroscopic constants for YbH and YbF obtained by this and other theoretical work are all in good agreement with available experimental data, the theoretical results for YbO show remarkable disagreement with each other and experiment. The present calculations favor a Ω=0+ ground state with a leading f14σ0 configuration, which is in agreement with the interpretation of experimental data. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475676
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  • 5
    Electronic Resource
    Electronic Resource
    Low-lying electronic states of lanthanocenes and actinocenes M(C8H8)2 (M=Nd, Tb, Yb, U) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 3584-3591 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Large-scale state-averaged multiconfiguration self-consistent field, multireference configuration interaction, and averaged coupled-pair functional calculations, including relativistic effects by means of energy-consistent quasirelativistic pseudopotentials, have been carried out for the ground and low-lying excited states of the di-π-cyclooctatetraene (or bis[8]annulene) metal sandwich complexes M(C8H8)2 (M=Nd, Tb, Yb, U). It is found that the ground state configurations for the lanthanocenes are 4fnπ3, while for the actinocenes they are 5fn−1π4. The ground states for the lighter and heavier lanthanocenes are, respectively, the lower and higher multiplicity states resulting from the coupling between the highest possible spin–multiplicity of the central metal 4fn subshell and the unpaired ligand π electron, whereas they always have the highest possible multiplicity of 5fn−1π4 for the actinocenes. The metal–ring distances and symmetric metal–ring stretching frequencies are reported. The special characteristics of the uranium 5f orbitals in uranocene are described. Extensive spin–orbit configuration interaction calculations were performed for uranocene and confirm the assignment of the ground state and first excited state of uranocene made previously by other authors. However, a different ordering is obtained for the higher states. The calculated term energy for the first excited state of uranocene is in excellent agreement with the experimental value. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474698
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  • 6
    Electronic Resource
    Electronic Resource
    Spectroscopic constants of MH and M2 (M=Tl, E113, Bi, E115): Direct comparisons of four- and two-component approaches in the framework of relativistic density functional theory (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 3626-3634 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The two-component DFT-ZORA (density functional theory, zeroth order regular approximation) method is implemented into the BDF (Beijing four-component density functional) program package so that systematic and direct comparisons between two- and four-component approaches are made possible for the first time. Different implementations of the ZORA method are also compared in this work. The calculated spectroscopic constants (bond lengths, binding energies, and force constants) for MH and M2 (M=Tl, E113, Bi, E115) by the two- and four-component approaches are very similar. The ionization and excitation energies for the metals obtained by these methods also agree very well with each other. Still, minor higher order relativistic effects beyond ZORA can be identified occasionally, but can be "safely" neglected. Therefore, the applicability of transformed (two-component) Hamiltonians to valence properties is well justified. However, the computational efficiency of four-component DFT compares favorably with that of two-component DFT. The problems of symmetry breaking and different treatments of open-shell systems are discussed by taking the Bi atom as an example. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1446026
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  • 7
    Electronic Resource
    Electronic Resource
    Comment on "Four-component relativistic density functional calculations of heavy diatomic molecules" [J. Chem. Phys. 112, 3499 (2000)] (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 2506-2507 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The present solid analysis shows that the results by Varga et al. [J. Chem. Phys. 112, 3499 (2000)] are not benchmark to calibrate more approximate relativistic approaches. The convergence of the multipolar expansion of the charge density to evaluate the Hartree potential is demonstrated. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.482070
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  • 8
    Electronic Resource
    Electronic Resource
    Erratum: "Spectroscopic constants of gold and eka-gold (element 111) diatomic compounds: The importance of spin-orbit coupling" [J. Chem. Phys. 110, 3730 (1999)] (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 891-891 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481865
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  • 9
    Electronic Resource
    Electronic Resource
    A method for population and bonding analyses in calculations with extended basis sets (1997)
    Springer
    Theoretical chemistry accounts 95 (1997), S. 81-95 
    Details
    ISSN: 1432-2234
    Keywords: Population analysis ; Bond order ; AOIM ; Basis set
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for population and bonding analyses in the calculations with extended basis sets is proposed. The definition and evaluation method of the atomic orbitals in molecular environments (AOIMs) are described. It is shown that the AOIMs can be divided into two subsets, the strongly occupied minimal compact subset {AOIM}B and the very weakly occupied “Rydberg” subset {AOIM}R, according to the orbital population obtained from Mulliken analysis with AOIMs as basis sets. The viewpoint of “molecular orbitals consisting of minimal atomic orbital sets” can be optimally realized in terms of {AOIM}B. The Mulliken population based on AOIMs is reasonable and fairly stable to changes of basis sets. The Mayer bond orders calculated based on {AOIM}B are quite stable to the changes of basis sets; therefore they can be used to measure objectively the contribution of individual atomic orbitals to bonding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02341693
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  • 10
    Electronic Resource
    Electronic Resource
    The Beijing four-component density functional program package (BDF) and its application to EuO, EuS, YbO and YbS (1997)
    Springer
    Theoretical chemistry accounts 96 (1997), S. 75-83 
    Details
    ISSN: 1432-2234
    Keywords: Key words: Relativistic effects ; Density functional theory ; Beijing Density Functional ; Lanthanide diatomics ; Atomic orbitals in molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. A four-component density functional program package (Beijing Density Functional), suitable for the calculation of total-energy-related chemical properties of systems containing heavy atoms, was developed. The code is based on modern sophisticated exchange-correlation functionals and was applied to calculate the spectroscopic constants of the lanthanide diatomic molecules of EuO, EuS, YbO and YbS. It is suggested that the experimental bond lengths for EuS and YbS, derived from empirical interpolations, need to be revised. Relativistic effects on the electronic structure are discussed and compared with results from previous work. The involvement of the lanthanide valence orbitals in chemical bonding is investigated with a newly developed population and bonding analysis approach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002140050207
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