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  • 1
    Electronic Resource
    Electronic Resource
    Correlation effects in externally perturbed many-electron systems (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 147-167 
    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: Different methods for the calculation of the electron correlation contribution to atomic and molecular properties are analyzed and evaluated. The methods based on the self-consistent solution of the external perturbation problem are shown to offer several formal and computational advantages. The analysis of the correlation perturbation series for properties of many-electron systems indicates the importance of the appropriate treatment of unlinked diagrammatic contributions. In particular, the standard limited configuration interaction scheme based on single and double substitutions in the reference function may significantly suffer from the erratic treatment of unlinked clusters and needs to be corrected appropriately. The basis set choice for the calculation of highly accurate values of properties is also discussed. In order to circumvent the dimensionality problem the use of basis sets with explicit dependence on the external perturbation strength is recommended and methods for their choice and optimization are presented. A particular attention is paid to the many-body perturbation theory involving singly and doubly substituted intermediate states and based on the coupled Hartree-Fock solution for the one-electron perturbation problem. Different computational aspects of this method are discussed and compared with other techniques currently in use.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230116
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  • 2
    Electronic Resource
    Electronic Resource
    Variable basis sets in perturbation theory: Numerical finite perturbation versus analytic approach (1979)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 15 (1979), S. 147-167 
    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 consider the problem of determining variational, external-field-dependent corrections to nonoptimal zero-field nonlinear parameters. Both a direct analytic perturbation analysis and finite perturbation methods are described in a general way and in detail for the SCF approximation. The abstract theory is illustrated by reference to the results of several explicit calculations. Also, the sensitivity of the results to the choice of zero-field values is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560150203
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  • 3
    Electronic Resource
    Electronic Resource
    Time-dependence of wave functions and the calculation of transition intensities (1989)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 35 (1989), S. 409-423 
    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: The standard formalism of the perturbation theory for time-dependent perturbations follows from the assumption that the exact solution of the unperturbed time-independent problem is known. The consequences of this assumption are analyzed.Particular attention is given to the methods used for the evaluation of transition intensities. It is shown that the traditional intensity formula in most cases violates the assumptions underlying its derivation. It is shown that for the given ansatz concerning the form of the approximate wave function, the transition intensities should be determined from the variation treatment of the corresponding time-dependent problem. The wave functions of both states involved in the transition should be given the same amount of variation flexibility. This condition is satisfied if the transition intensity expression follows from the complete timedependent perturbation treatment of the perturbed system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560350306
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  • 4
    Electronic Resource
    Electronic Resource
    Vibronic absorption spectrum of the ethylene dimer (1969)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 569-580 
    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: Vibronic coupling theory is used to construct the vibronic absorption spectrum of the ethylene dimer. It is shown that in this case an extended four-parameter form of the vibronic Hamiltonian should be considered. In addition to the commonly used three vibronic parameters, the difference between the ground and excited state force constants of the monomer is taken into account.Numerical calculations were performed for the dimer geometry resembling that of norbornadiene. Some comments on the interpretation of the absorption spectrum of norbornadiene are made.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560030504
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  • 5
    Electronic Resource
    Electronic Resource
    Analytic techniques for the coupled multiconfiguration SCF perturbation theory (1977)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 11 (1977), S. 233-245 
    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: The perturbation theory based on the paired excitation multiconfiguration self-consistent field approach of Clementi and Veillard is considered. The coupled first-order perturbed orbital equations are analysed and an appropriate computational scheme for their solution is discussed. The proposed computational scheme is analogous to the technique employed for the solution of the coupled Hartree-Fock equations in the one-configuration approximation. However, because of the presence ofnondiagonal Lagrangian multipliers and the use of different one-electron operators for different orbitals, the present scheme raises some new computational problems. In this context a new technique for the solution of the unperturbed multiconfiguration self-consistent field equations is proposed. A simple illustration of the superiority of the multiconfiguration perturbation approach with respect to the ordinary coupled Hartree-Fock scheme is given. Also the validity of the variation formulation of the presented scheme and its relation to the finite-field approach are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560110204
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  • 6
    Electronic Resource
    Electronic Resource
    Polarized basis sets for high-level-correlated calculations of molecular electric properties VIII. Elements of the group IIb: Zn, Cd, Hg (1995)
    Springer
    Theoretica chimica acta 91 (1995), S. 353-371 
    Details
    ISSN: 0040-5744
    Keywords: Key words: Polarized basis sets ; Electric dipole polarizabilities of Zn ; Cd ; Hg ; and their positive ions ; Electron correlation effects on atomic properties ; Relativistic effects on atomic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary. The first-order polarized basis sets are generated for Zn, Cd, and Hg and their performance is tested in high-level-correlated calculations of electric dipole polarizabilities of these atoms. The present results calculated at the level of the non-relativistic CCSD(T) approximation with 12 explicitly correlated electrons are: 40.4 a.u. for Zn, 56.3 a.u. for Cd, and 58.0 a.u. for Hg. Upon including the relativistic and electron correlation–relativistic corrections within the quasirelativistic scheme based on the mass–velocity and Darwin terms these values are reduced to 37.9 a.u., 47.6 and 31.8 a.u., respectively. The derived polarized basis sets have been also used for the evaluation of the dipole polarizability of singly and doubly positive ions of the group IIb elements and are recommended for calculations of interaction energies and interaction-induced electric properties in both neutral and charged systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133080
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  • 7
    Electronic Resource
    Electronic Resource
    Standardized basis sets for high-level-correlated relativistic calculations of atomic and molecular electric properties in the spin-averaged Douglas–Kroll (no-pair) approximation I. Groups Ib and IIb (1996)
    Springer
    Theoretica chimica acta 94 (1996), S. 93-104 
    Details
    ISSN: 0040-5744
    Keywords: Key words: Polarized basis sets ; Relativistic effects ; Douglas ; Kroll no-pair approximation ; Dipole polarizabilities of Zn ; Cd ; Hg ; Dipole moments of CuH ; AgH ; and AuH ; Polarizabilities of atomic ions: Cu+ ; Ag+ ; Zn2+ ; Cd2+ ; Hg2+
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  The technique developed earlier for the generation of the so-called first-order polarized basis sets for accurate non-relativistic calculations of molecular electric properties is used to obtain similar basis sets suitable for calculations in the Douglas–Kroll no-pair approximation. The corresponding (relativistic) basis sets are devised for atoms of the Groups Ib and IIb of the periodic table and tested in calculations of atomic polarizabilities and dipole moments of the coinage metal hydrides. Excellent performance of these basis sets has been found in the case of molecular calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194934
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