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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 8969-8975 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have calculated bond lengths, harmonic vibrational frequencies, and dissociation energies for (117)H, (113)H, and (113)F using relativistic effective core potentials (RECPs) with one-electron spin–orbit operators at the two-component coupled-cluster levels of theory. It is shown that any reasonable theoretical descriptions of the electronic structures of molecules containing superheavy elements require consideration of relativistic interactions and electron correlations. Comparisons with available all-electron Dirac–Fock (DF) based results indicate that our two-component approaches are very promising tools in the calculations for the molecules containing superheavy elements. The spin–orbit effects calculated from one- and two-component RECPs are in good agreement with those from all-electron Douglas–Kroll and DF results, implying that the potential average scheme is useful for obtaining one-component RECPs even for superheavy elements. Spin–orbit and electron correlation effects are not additive for molecular properties of (117)H, (113)H, and (113)F, but spin–orbit effects are qualitatively similar at all levels of theory considered. Spin–orbit effects contract Re and increase ωe for (113)H and (113)F, whereas they expand Re and decrease ωe for (117)H. Spin–orbit effects decrease De for all molecules considered, but the amount of decrease for (113)H and (117)H is substantially smaller than that estimated from the atomic splittings. For (117)H, our best calculations yield 1.983 Å (Re), 1403 cm−1(ωe), and 1.60 eV (De). © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The spin–orbit effects for Tl, TlH, TlH3, PbH2, and PbH4 are evaluated by two-component calculations using several relativistic effective core potentials (RECP) with one-electron spin–orbit operators. The used RECPs are shape-consistent RECPs derived by Wildman et al. [J. Chem. Phys. 107, 9975 (1997)] and three sets of energy-consistent (or adjusted) RECPs published by Schwerdtfeger et al. [Phys. Scr. 36, 453 (1987); J. Chem. Phys. 90, 762 (1989)], Küchle et al. [Mol. Phys. 74, 1245 (1991)], and Leininger et al. [Chem. Phys. 217, 19 (1997)]. The shape-consistent RECP results are in very good agreement with the Küchle et al. energy-consistent RECP results for all the molecules studied here and all-electron results for TlH. The RECPs of Schwerdtfeger et al. and Leininger et al. seem to provide qualitatively different spin–orbit effects. If one defines spin-free RECP as the potential average of the corresponding two-component RECP, all RECPs give very similar spin–orbit effects for all the cases. Most of the discrepancies of molecular spin–orbit effects among various RECPs reported in the literature may originate from different definitions of RECPs with or without a spin–orbit term and not from the inherent difference in spin–orbit operators. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Kramers' restricted Hartree-Fock (KRHF) and second-order Møller-Plesset perturbation (KRMP2) methods using relativistic effective core potentials (RECP) with spin-orbit operators and two-component spinors are extended to the unrestricted forms, KUHF and KUMP2. As in the conventional unrestricted methods, the KUHF and KUMP2 methods are capable of qualitatively describing the bond breaking for a single bond. As a result, it is possible to estimate spin-orbit effects along the dissociation curve at the HF and MP2 levels of theory as is demonstrated by the test calculations on the ground states of HI and CH3I. Since the energy lowering due to spin-orbit interactions is larger for the I atom than for the closed-shell molecules, dissociation energies are reduced and bond lengths are slightly elongated by the inclusion of the spin-orbit interactions.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66: 91-98, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1526-1533 
    ISSN: 0192-8651
    Keywords: geometry optimization ; spin-orbit effect ; two-component calculation ; effective core potential with one-electron spin-orbit operator ; photoelectron spectra ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We have implemented geometry optimization using an analytic gradient to a two-component Kramers' restricted Hartree-Fock (KRHF) method for polyatomic molecules with closed-shell configurations. The KRHF method is a Hartree-Fock method based on relativistic effective core potentials with effective spin-orbit operators. The derivatives of spin-orbit integrals are obtained by numerical differentiation. Geometries for the various forms of polyatomic hydrides containing row 6 p-block elements are optimized with and without spin-orbit interactions. The structural changes due to spin-orbit interactions are small, but show definite trends, which correlate well with the p1/2 spinor population. Atomization energies are reduced significantly by incorporating spin-orbit interactions for all molecules considered. The KRHF calculations of several methylhalides demonstrate that the spinor energies from the KRHF method can be useful for the interpretation of experimental photoelectron spectra of molecules exhibiting spin-orbit splittings.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 1526-1533, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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