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  • 1
    Digitale Medien
    Digitale Medien
    Laplace transform techniques in Møller–Plesset perturbation theory (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 489-494 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We discuss how the computational obstacles related to energy denominators in various schemes for electron-correlation calculations can be circumvented by a Laplace transform technique. The method is applicable to a wide variety of electronic structure calculations. We discuss in detail an algorithm for the contribution of triple excitations in fourth-order Møller–Plesset perturbation theory, which grows only with the sixth power of the size of the system, as compared to conventional N7 algorithms. Special consideration is given to efficient schemes for numerical quadrature of the integrals occurring in the Laplace transformations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.462485
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  • 2
    Digitale Medien
    Digitale Medien
    Molecular point-group symmetry in electronic structure calculations (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 8259-8265 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A generalization of Pitzer's equal contribution theorem is put forth. The new theorem specifies which types of matrix elements can be constructed using only symmetry-unique (batches of) integrals. A general and simple algorithm to use molecular point-group symmetry in electronic structure calculations is outlined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.461305
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  • 3
    Digitale Medien
    Digitale Medien
    A direct algorithm for self-consistent-field linear response theory and application to C60: Excitation energies, oscillator strengths, and frequency-dependent polarizabilities (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 1262-1270 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We present a direct self-consistent-field (SCF)-type algorithm and its implementation for the computation of linear response properties: excitation energies, oscillator strengths, and frequency-dependent polarizabilities within the time-dependent SCF or random phase approximation. The treatment of singles configuration interaction for electronic excitations and Hartree–Fock instability criteria are covered as special cases. The algorithm is based on proven direct SCF methodology. This, together with full exploitation of molecular symmetry, opens the way to the treatment of large molecules. Applications to C60 strongly support the assignment of the lowest-lying dipole allowed transition to the strong band at 3.8 eV.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.465370
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  • 4
    Digitale Medien
    Digitale Medien
    Calculated properties of P2, P4, and of closed-shell clusters up to P18 (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3703-3711 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The thermodynamic stabilities of the most stable even-membered and electrically neutral molecules (clusters) of phosphorus P2 through P18 are calculated in high accuracy. The larger clusters Pn, n(approximately-greater-than)4, turn out to be unstable at elevated temperatures, but are thermodynamically stable with respect to decay into P4 at low temperatures. To aid an experimental identification of such clusters, calculated vibrational frequencies, ionization potentials, and electronic excitation energies are supplied. As a side result we find the equilibrium bond length in P4 to be substantially shorter (below 220 pm) than the established experimental value r0=222.28±0.05 pm. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.468552
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  • 5
    Digitale Medien
    Digitale Medien
    Electron correlation in tetrapyrroles: ab initio calculations on porphyrin and the tautomers of chlorin (1993)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 10964-10970 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100144a012
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  • 6
    Digitale Medien
    Digitale Medien
    Structural Rules of Phosphorus (1994)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 116 (1994), S. 6925-6926 
    Details
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ja00094a053
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  • 7
    Digitale Medien
    Digitale Medien
    Non-Abelian point group symmetry in direct second-order many-body perturbation theory calculations of NMR chemical shifts (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 8295-8301 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A scheme that fully exploits molecular point group symmetry in direct second-order many-body perturbation theory chemical shift calculations based on gauge-including atomic orbitals is presented and implemented. Representative calculations for the molecules B4(tBu)4 (Td symmetry) and [AlCp]4 (D2d symmetry) involving more than 600 basis functions demonstrate the applicability of the developed program to large symmetric molecules (which could be otherwise not treated) and indicate the importance of electron correlation effects for the reliable prediction of NMR chemical shifts in larger molecules. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.476258
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  • 8
    Digitale Medien
    Digitale Medien
    Clusters of phosphorus: a theoretical investigation (1992)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 114 (1992), S. 9551-9559 
    Details
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ja00050a039
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  • 9
    Digitale Medien
    Digitale Medien
    Theoretical investigation of next neighbour interactions and ring strain in linear and monocyclic phosphanes (1989)
    Springer
    Theoretical chemistry accounts 75 (1989), S. 1-10 
    Details
    ISSN: 1432-2234
    Schlagwort(e): Phosphanes ; Structure of phosphanes ; Ring strain ; Lone pair interactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The molecules PH3, P2H4, P3H5, P3H3, P4H4, and P5H5 were treated at the SCF level using basis sets of DZP quality. Computed structure constants and energies indicate high stability for P5-ring systems and small ring strain for P3- and P4-ring systems. The computed values for the strain are 28 and 18 kJ/mol for P3H3 and P4H4, respectively. Neighbouring P atoms with transconfigured lone pairs are favoured in the monocyclic phosphanes considered in this work, as shown by the energy difference of about 10 kJ/mol between trans and cis configured lone pairs, and the shortening of P-P distances by about 2 pm for trans configured P atoms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01151229
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  • 10
    Digitale Medien
    Digitale Medien
    RI-MP2: first derivatives and global consistency (1997)
    Springer
    Theoretical chemistry accounts 97 (1997), S. 331-340 
    Details
    ISSN: 1432-2234
    Schlagwort(e): Key words: Gradients ; Perturbation theory of electronic structure ; MP2 ; Electron correlation ; Coulomb interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract. The evaluation of RI-MP2 first derivatives with respect to nuclear coordinates or with respect to an external electric field is described. The prefix RI indicates the use of an approximate resolution of identity in the Hilbert space of interacting charge distributions (Coulomb metric), i.e., the use of an auxiliary basis set to approximate charge distributions. The RI technique is applied to first derivatives of the MP2 correlation energy expression while the (restricted) Hartree-Fock reference is treated in the usual way. Computational savings by a factor of 10 over conventional approaches are demonstrated in an application to porphyrin. It is shown that the RI approximation to MP2 derivatives does not entail any significant loss in accuracy. Finally, the relative energetic stabilities of a representative sample of closed-shell molecules built from first and second row elements have been investigated by the RI-MP2 approach, and thus it is tested whether such properties that refer to potential energy hypersurfaces in a more global way can be described with similar consistency to the more locally defined derivatives.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002140050269
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