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  • 1
    Electronic Resource
    Electronic Resource
    The dipole moment of carbon monoxide (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6660-6663 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dipole moment of CO has been calculated with many-body perturbation theory (MBPT) and coupled cluster (CC) methods using basis sets which have been optimized at the MBPT-2 level. It is demonstrated that triple excitations as well as g-type functions in the basis set are crucial to obtain satisfactory agreement with experiment. The most reliable prediction (0.125 D) is obtained at the CCSD(T) (coupled cluster including all single, double, and connected triple excitations, perturbatively) level of theory using a 10s9p4d2f1g basis set (160 basis functions). This result is in excellent agreement with the experimental value of 0.122 D.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460293
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  • 2
    Electronic Resource
    Electronic Resource
    The electric dipole moment of ArH+. Disagreement between theory and experiment (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6486-6490 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The experimentally determined dipole moment of the ArH+ molecular ion (1.4 D, 1.59 D) is in considerable disagreement with previous ab initio calculations (2.2 D). In this work we present further theoretical evidence strongly supporting a dipole moment of 2.1±0.1 D. We have carried out an extensive basis set study and calculated the dipole moment using the coupled cluster analytical energy gradient and polarization propagator techniques. Based on a theoretical determination of the equilibrium rotational g factors for ArH+ and ArD+ we conclude that the extrapolation of the experimentally determined g factors to their equilibrium values is the main source of the discrepancy between theory and experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456314
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  • 3
    Electronic Resource
    Electronic Resource
    A solution of the gauge origin problem for the magnetic susceptibility (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4892-4894 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A polarization propagator based theory for calculation of the diamagnetic part of the magnetic susceptibility is presented. Since the paramagnetic term also may be obtained from the propagator it is thus possible to compute both contributions at the same level of approximation, e.g., in RPA, SOPPA, and CCPPA. Contrary to other commonly used procedures the present method gives a total result for the susceptibility, which—even in a limited basis set—is independent of the origin chosen for the vector potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456583
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  • 4
    Electronic Resource
    Electronic Resource
    Spin–spin coupling constants of CO and N2 (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 2138-2142 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have used the second order polarization propagator method to calculate the indirect nuclear spin–spin coupling constants of 13C–17O and 14N–15N. We have calculated all coupling terms and the vibrationally averaged results are for CO: JFC =7.93 Hz, JSD =−3.99 Hz, JPSO =14.95 Hz, JDSO =0.10 Hz, Jtotal(CO) =18.99 Hz and for N2: JFC =0.82 Hz, JSD =−1.57 Hz, JPSO =3.32 Hz, JDSO =0.03 Hz, and Jtotal(N2) =2.60 Hz. Recent measurements of the two coupling constants gave 1J(13C,17O)=16.4±0.1 Hz and 1J(14N,15N)=1.8±0.6 Hz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453722
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  • 5
    Electronic Resource
    Electronic Resource
    Nuclear magnetic shieldings and spin rotation constants of HF and N2 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 6036-6042 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The paramagnetic contribution to the nuclear magnetic shieldings and the spin rotation constants are calculated using polarization propagator theory. Results are reported both in the first order approximation [equivalent to the coupled Hartree–Fock (CHF) method] and in the second order polarization propagator approximation (SOPPA). It is demonstrated how the constant Cgauge which gives the gauge origin dependence of the total nuclear magnetic shielding in a finite basis set [σ(Rc+d)=σ(Rc)+d⋅Cgauge] can be calculated from the polarization propagator. The magnetic shieldings of H and F in HF are nearly the same in CHF and SOPPA and results from both levels of theory agree well with experiment. For N2, σ(SOPPA)=−72.2 ppm, also in good agreement with the most recent measurement. However, for N2 there is a large correlation effect since σ(CHF)=−106.5 ppm. The computed spin rotation constant for N2 is M(15N)=20 kHz, i.e., about 2 kHz lower than its measured value. This value of M(15N) corresponds to σ(N)=−72.2 ppm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458375
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  • 6
    Electronic Resource
    Electronic Resource
    The calculation of electric dipole moments from the polarization propagator. Theory and application (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 364-367 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A method for computation of dipole moments from the polarization propagator is presented and applied to the H2O molecule. Using extended basis sets it is shown that the coupled cluster singles doubles polarization propagator approximation (CCSDPPA) reproduces the experimental dipole moment to a high degree of accuracy
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457468
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic spectra and response properties of BH and AlH (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2338-2343 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have calculated ground-state potential-energy curves, vertical electronic excitation energies, transition moments, radiative lifetimes, and indirect nulcear spin–spin coupling constants of BH and AlH. The coupling constants are predicted to be J(11B–H)=49.40 Hz and J(27Al–H)=10.01 Hz. Total energies are obtained using the coupled clusters singles and doubles method while excitation energies and response properties are calculated by means of the coupled cluster polarization propagator method. It is essential for the agreement with experiment that the coupled cluster rather than the second-order polarization propagator method is applied. The lowest excitation energies of each symmetry are nearly the same in a CISD (CI singles and doubles) calculation as in the polarization propagator calculation and both methods agree well with experiment. However, orbitals optimized for the individual states are needed in the CISD calculation, whereas ground-state self-consistent field (SCF) orbitals may be used for all states in the propagator calculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455975
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  • 8
    Electronic Resource
    Electronic Resource
    A coupled cluster polarization propagator method applied to CH+ (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 2112-2118 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new approach to the direct evaluation of excitation energies and transition moments from the polarization propagator is presented. The method, which uses a coupled cluster doubles (CCD) reference state within the framework of perturbative propagator methods, is applied to the lowest singlet and triplet excitations in CH+. Comparison of the coupled cluster doubles polarization propagator approximation (CCDPPA) results with experiments and standard perturbative polarization propagator calculations shows that a significant improvement is obtained with a coupled cluster rather than a Rayleigh–Schrödinger reference state: the singlet excitation energy is improved by about 0.5 eV and the triplet instability of the standard second order approach is removed. The radiative lifetime of the v'=0 level of the A 1Π state is estimated to be very close to 800 ns. The improved performance of the coupled cluster propagator method over propagator calculations based on Rayleigh–Schrödinger expansion mainly stems from a enhancement of the correlation coefficients for the lower double excitations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451156
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  • 9
    Electronic Resource
    Electronic Resource
    Nuclear spin-spin coupling constant of hydrogen molecule with deuterium (HD) (1988)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 92 (1988), S. 3056-3059 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100322a009
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  • 10
    Electronic Resource
    Electronic Resource
    Calculation of spectra and spin-spin coupling constants using a coupled-cluster polarization propagator method (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 475-485 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present a coupled-cluster polarization propagator method based on a coupled cluster singles and doubles reference state. Applications to the Be atom show that we may calculate electronic excitation energies with an average absolute error of about 0.08 eV using this method. We have also calculated the nuclear spin-spin coupling constant of 1H19F to be 524.4 cps, in good agreement with experiment. For Be there is a large effect of using coupled-cluster rather than a low-order Rayleigh-Schrödinger expansion, whereas the coupling constant of HF is less sensitive to this improvement in the reference state.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320746
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