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  • 1
    Electronic Resource
    Electronic Resource
    One-center integrals of the exact effective valence shell Hamiltonian. Empirical analysis for atoms (1980)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 102 (1980), S. 1270-1277 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00524a009
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  • 2
    Electronic Resource
    Electronic Resource
    The multiconfigurational spin tensor electron propagator method (MCSTEP): Electron affinities of Li, Na, and K (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5451-5454 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The multiconfigurational spin tensor electron propagator approximation to the electron propagator is applied for the first time to the calculation of electron affinities. The electron affinities of Li, Na, and K are calculated as the ionization potentials of the negative ions. On average these electron affinities differ from experiment by 0.003 eV, giving the best theoretical values reported to data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457546
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  • 3
    Electronic Resource
    Electronic Resource
    Application of the multiconfiguration time-dependent Hartree–Fock method to CH+: The auxiliary active space (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 3063-3070 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The multiconfigurational time-dependent Hartree–Fock (MCTDHF) method is used to study the excitation energies and transition moments of the CH+ ion. A consistent approach to the selection of configurations based on the complete active space (CAS) model is successfully applied. In this approach a large set of orbitals is included in the active space without a substantial increase in the number of configurations, since only for a smaller subset of orbitals is the configuration expansion complete and the remaining orbitals active are considered an auxiliary set. For CH+ the active space includes the valence and additional orbitals, with the valence orbitals constituting the complete subset. Extra configurations involving single and double excitations from the valence to the additional (auxiliary) orbitals are included both for the MCSCF reference state and in the MCTDHF. It is demonstrated that this active space accurately mimics MCSCF and MCTDHF calculations with an enlarged complete active space which includes both the original CAS and the auxiliary orbitals. The calculations for the 1 Π and 1 Σ+ excited states at the equilibrium geometry show that accurate excitation energies and transition moments are obtained in this way. For most of these states for which there are other good ab initio results available, we obtain comparable excitation energies and transition moments. In addition to 1 Π and 1 Σ+ , low lying states of other symmetries are obtained and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454962
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  • 4
    Electronic Resource
    Electronic Resource
    Erratum: The ionization potentials of F2: A comparison of multiconfigurational electron propagator (MCEP) with other large scale methods using the same basis set [J. Chem. Phys. 84, 284 (1986)] (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 778-778 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453757
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  • 5
    Electronic Resource
    Electronic Resource
    Characteristics and some peculiarities of multiconfigurational self-consistent field stationary points of the Li− ground state (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8011-8020 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We examine in detail the multiconfigurational self-consistent field (MCSCF) energy hypersurface of the ground state of Li− using a previously reported Cartesian Gaussian basis set and several previously used different choices of complete active space (CAS). For many of the CASs we show there are many close-lying (in energy) stationary points that have the correct number of negative eigenvalues in the total Hessian with respect to real variations of the orbital and configurational parameters and correspond to the lowest energy eigenvector in the configuration interaction (CI) which uses the MCSCF orbitals and configurations. These stationary points may be obtained with any of the current, forefront MCSCF codes. More detailed examination of these stationary points shows that some of these are improper and that some do not correspond to the most "desired'' stationary point. The presence of two nearby proper, desired MCSCF stationary points with the 2–3s, 2–3p CAS is troubling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459330
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  • 6
    Electronic Resource
    Electronic Resource
    Erratum: The multiconfigurational spin tensor electron propagator method: Electron affinities of Li, Na, and K [J. Chem. Phys. 91, 5451 (1989)] (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 6336-6337 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458607
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  • 7
    Electronic Resource
    Electronic Resource
    The ionization potentials of NH2: The multiconfigurational spin-tensor electron propagator method (MCSTEP) applied to a polyatomic open-shell radical (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 2572-2581 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The multiconfigurational spin-tensor electron propagator method (MCSTEP) gives accurate ionization potentials (IPs) and electron affinities (EAs) for both closed-shell and open-shell molecules, including for highly correlated systems. Both principal and lower-lying shakeup IPs can be accurately obtained and straightforwardly characterized using MCSTEP. To further test this new technique, we have applied the MCSTEP approach to the open-shell, polyatomic radical NH2. We report and characterize vertical IPs 0–20 eV, including several ionizations that have not, as yet, been observed experimentally. IPs to both singlet and triplet states of NH+2 are accurately calculated using the same MCSCF reference state. We predict the presence of previously undetected, observable vertical PES IPs to states of 3A2, 1A1, and 1A2 symmetries at 16.86, 18.00, and 18.26 eV, respectively. Also, we calculate adiabatic IPs by a modified application of the procedure. By examining the two lowest adiabatic IPs with both MCSTEP and Δmultireference singles+doubles CI at geometries established by Pople's research group and with the basis set used by that group augmented by hydrogen d polarization functions we conclude that their MP4 procedures overestimate the IPs with their best basis set by ∼0.2–0.3 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454037
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  • 8
    Electronic Resource
    Electronic Resource
    The multiconfigurational spin-tensor electron propagator method for determining vertical principal and shake-up ionization potentials for open shell and highly correlated atoms and molecules (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 2925-2944 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We propose and develop the multiconfigurational spin-tensor electron propagator (MCSTEP) technique for the theoretical determination of vertical ionization potentials (IPs) and electron affinities (EAs) for general open-shell and highly correlated atoms and molecules. We obtain these equations from a Green's function or electron propagator approach where we properly couple electron removal and addition tensor operators to a multiconfigurational tensor state. To account for important shake-up effects and to achieve a "balance'' in initial and final state correlation corrections, we include in MCSTEP ionization and electron affinity operators analogous to the ||c〉〈0|| state transfer operators necessary in multiconfigurational linear response. In repartitioned MCSTEP (RMCSTEP) we augment the MCSTEP operator manifold with operators of the form a+iajak by first employing partitioning theory to estimate their contributions and then repartitioning only the important operators into the primary space. In this way, important shake-up processes to diffuse orbitals are accurately and reliably handled with RMCSTEP at the same level of approximation, i.e., as part of the primary space operator manifold . Initial application of these methods is extremely encouraging for both principal and shake-up IPs. Using a 〈5s5pld〉 contracted Gaussian valence basis set augmented with two diffuse s, two diffuse p, and two diffuse d functions, the RMCSTEP ionization potentials to the low-lying (〈∼24 eV) 2S and 2P bound ionic states (including diffuse states) for Be are calculated within ±0.07 eV of experiment. The IP to the lowest 2D state is calculated 0.14 eV from experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453081
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  • 9
    Electronic Resource
    Electronic Resource
    The multiconfigurational particle–particle propagator method for directly determining vertical double ionization potentials and double electron affinities (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 2884-2893 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present and develop the multiconfigurational particle–particle propagator (MCP2P) method for directly determining vertical double ionization potentials (DIPs) and double electron affinities. The MCP2P method gives highly accurate DIPs. In the first calculations with this method (obtained using a moderate-sized MCP2P complete active space) the average absolute deviation from Δfull configuration interaction within the same basis set for the DIPs to the lowest (in energy) five 1,3S Be2+ states is 0.04 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459810
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  • 10
    Electronic Resource
    Electronic Resource
    Accurate transition moments between the A 3Σ+u, B 3Πg, and B' 3Σ−u of N2 using multiconfigurational linear response (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1533-1539 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Accurate values of the electronic transition moment function for the first positive (A 3∑+u−B 3Πg) and infrared afterglow (B 3Πg −B'3∑−u) systems of N2 were obtained through multiconfigurational linear response (also known as the multiconfigurational time-dependent Hartree–Fock, MCLR/MCTDHF). MCLR/MCTDHF furnished both excitation energies and transition moments. MCLR/MCTDHF calculations on the first positive system demonstrate the importance of configurations involving the 2σg orbital. To obtain accurate values, configurations were chosen with a complete active space of all valence orbitals (2σg, 2σu, 1πu, 3σg, 1πg, 3σu). This is the first MCLR/MCTDHF calculation for molecules as large as first row diatomics in which a complete active space including the entire valence shell is employed. The results are in substantial agreement with accurate theoretical calculations by others and, hence, disagree in their overall behavior with the previously published empirical values. One of our conclusions is that the experimental values for the first positive system far from the equilibrium region are in error.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455151
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