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  • 1
    Electronic Resource
    Electronic Resource
    Structure and stability of Na6Pb clusters (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 6613-6617 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The geometric and electronic structures of the bimetallic cluster, Na6Pb, have been calculated using the density functional and coupled-cluster approaches, with a relativistic effective core potential and one-electron spin–orbit operators. Six possible isomeric Na6Pb structures (Oh, D3h, D3d, C5v, C3v, and C2v) have been examined, and the highly symmetrical Oh structure was found to be the most stable form. The stabilities of the clusters correlate well with the Pb–Na bond distances and with the charge transfer from the Na6 subsystem to the more electronegative Pb atom. The binding energies were found to vary according to the structure, with a spread of about 0.1 eV and 0.3 eV for the density functional and coupled-cluster calculations, respectively. These are of the same order, and somewhat smaller, as are found for the Na6Mg clusters (about 0.5 eV), demonstrating that the stabilization of the Na6Pb cluster is not particularly dependent on the geometric structures. At the same time, we found that the Na6Pb cluster is more stable as the symmetry is higher. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1311298
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  • 2
    Electronic Resource
    Electronic Resource
    On the ground-state spectroscopic constants of Tl2 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 9353-9355 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ground-state Re, ωe, and De of Tl2 are evaluated using the multireference Kramers' restricted configuration interaction method with relativistic effective core potential and spin–orbit operators. The best computed (estimated) values are 3.11 (3.05) Å, 75 (79) cm−1, and 0.34 (0.38) eV. These results are in accordance with the Raman experimental data of 3.0 Å, 78 cm−1, and 0.43±0.04 eV(D0) for Re, ωe, and De, respectively. The relevant treatment for nondynamic correlations is necessary to obtain reliable spectroscopic constants, although the spin–orbit operators are introduced from the Hartree–Fock stage. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481555
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  • 3
    Electronic Resource
    Electronic Resource
    Density functional studies of UO22+ and AnF6 (An=U, Np, and Pu) using scalar-relativistic effective core potentials (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 7345-7350 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have performed one-component relativistic calculations to determine the bond lengths and harmonic vibrational frequencies of UO22+ and AnF6 (An=U, Np, and Pu) using various density functional calculations with relativistic effective core potentials (RECPs) and extended basis sets. The calculated spectroscopic constants using small-core RECPs compare favorably with the available all-electron relativistic results for UO22+ and UF6. The results using the hybrid functionals are in very good agreement with the experimental data for the geometries and vibrational frequencies of the AnF6 systems. The performance of pure gradient-corrected functionals is poor, even worse than that of local density functional for the geometries and vibrational frequencies. For the vibrational frequencies, the hybrid functional calculations give qualitatively the correct order with small quantitative deviations from the experimental data. The local density functional provides reliable frequencies for the stretching modes but underestimates the frequencies for the bending modes. The pure gradient-corrected functionals underestimate the frequencies for all the stretching and bending modes. While the large-core RECP calculations provide short bond lengths and a rather poor description for vibrational frequencies relative to small-core RECP calculations for UO22+ and UF6, they may still be a practical choice of method provided hybrid functionals are also used, especially for larger systems. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1312827
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  • 4
    Electronic Resource
    Electronic Resource
    Spin–orbit effects on the transactinide p-block element monohydrides MH (M=element 113–118) (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2684-2691 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Spin–orbit effects on the bond lengths and dissociation energies of sixth- and seventh-row p-block element monohydrides MH(M=Tl–Rn and element 113–118) are evaluated using relativistic effective core potentials at the coupled-cluster level of theory. Spin–orbit effects play a dominant role in the determination of molecular properties for the seventh-row hydrides. Spin–orbit effects on the bond lengths and dissociation energies of seventh-row hydrides are qualitatively similar to, but substantially larger than those of the sixth-row homologs due to the enormous spin–orbit splitting of 7p orbitals. Spin–orbit interactions change the bond lengths of sixth- and seventh-row hydrides by −0.02∼+0.03 Å and −0.21∼+0.21 Å , respectively. Spin–orbit interactions usually elongate the bond lengths except for the molecules of the (p1/2)1-valence atoms, i.e., TlH and (113)H. The maximum elongation is predicted for (115)H, where the element 115(eka-bismuth) has the (7p3/2)1 configuration outside the inner (7p1/2)2 closed-shell. The spin–orbit coupling weakens the bondings between the heavy element and the hydrogen except for BiH and changes the dissociation energies by −0.71∼+0.08 eV and −2.18∼−0.23 eV for sixth- and seventh-row hydrides, respectively. The dissociation energy of the (114)H molecule is merely 0.39 eV, because the element 114(eka-lead) has a closed-shell electronic structure in the jj-coupling scheme. The bonding between the element 118(eka-radon), which is another closed-shell atom, and hydrogen is very weak and can be regarded as a pure van der Waals bond. But with highly electronegative elements the element 118 seems to form more stable compounds than other closed-shell atoms such as the element 112(eka-mercury) or the element 114. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480842
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  • 5
    Electronic Resource
    Electronic Resource
    Two-component calculations for the molecules containing superheavy elements: Spin–orbit effects for (117)H, (113)H, and (113)F (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 8969-8975 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.478814
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  • 6
    Electronic Resource
    Electronic Resource
    On the consistent definition of spin–orbit effects calculated by relativistic effective core potentials with one-electron spin–orbit operators: Comparison of spin–orbit effects for Tl, TlH, TlH3, PbH2, and PbH4 (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 9353-9359 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.478901
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  • 7
    Electronic Resource
    Electronic Resource
    Kramers' unrestricted Hartree-Fock and second-order Møller-Plesset perturbation methods using relativistic effective core potentials with spin-orbit operators: Test calculations for HI and CH3I (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 66 (1998), S. 91-98 
    Details
    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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  • 8
    Electronic Resource
    Electronic Resource
    Spin-orbit effects on structures of closed-shell polyatomic molecules containing heavy atoms calculated by two-component Hartree-Fock method (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1526-1533 
    Details
    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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