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  • 1
    Electronic Resource
    Electronic Resource
    Electronic state representations at molecular potential pseudocrossingsWork partially supported by National Science Foundation Grant Nos. CHE 77-20510 and CHE 80-19510 (1982)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 22 (1982), S. 971-988 
    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: A diabatic representation is introduced to describe electronic states around adiabatic pseudocrossings, as an alternative to presently available representations. A transformation from the adiabatic to the new diabatic representation is chosen to assure well behaved diabatic potentials for arbitrary momentum coupling strengths. Parameters of the transformation are determined by minimizing momentum couplings in the pseudocrossing region. The problem of two electronic states in one relative position variable is treated in detail and is studied with a numerical model. A comparison of results of our procedure and of other available ones is given. The present developments also provide a criterion for neglecting momentum couplings based on their strength and on the range of collision energies.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560220509
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  • 2
    Electronic Resource
    Electronic Resource
    Semiclassical time-correlation function approach to collisional energy transfer into many-atom systems (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 551-560 
    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: Cross sections for energy transfer into many-body systems can be expressed in terms of time-correlation functions (TCFS) of transition operators. A semiclassical version is presented by treating internal motions as quantized and relative motions as classical. The time evolution of internal motions can be calculated in the Heisenberg picture and avoids expansions in target states. The decoupling of fast and slow internal motions is treated and applied to vibrational-rotational decoupling in polyatomic molecules. Results are presented for Li+-CO2 collisions.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230225
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  • 3
    Electronic Resource
    Electronic Resource
    Collisional time correlation function approach to the interaction of light with a polyatomic system (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 229-237 
    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 interaction of light with a polyatomic system is treated as a photon-scattering process in terms of time-correlation functions of transition operators. These are written as products of factors referring only to the molecule or the light field, so that the statistical properties of the polyatomic system and the light source can be easily incorporated. This procedure is developed for resonance absorption-emission and scattering of both thermal and coherent light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320725
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  • 4
    Electronic Resource
    Electronic Resource
    Errata (1973)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 7 (1973), S. 635-636 
    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
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560070316
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  • 5
    Electronic Resource
    Electronic Resource
    Stable and efficient algorithms for Xα multiple scattering calculations (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 1091-1099 
    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: Solutions to some practical problems that arise in multiple scattering calculations on large molecules are discussed. (1) Numerical instabilities near the zero of energy can be removed by rescaling the secular matrix. (2) The calculation of structure factors can be made much more efficient by the application of symmetry projection operators. (3) An energy search procedure is described that ensures that no states are inadvertently neglected. Test calculations incorporating these changes illustrate the improved numerical stability, and show decreases in computation time of 30-60%, when compared to previous codes. The procedures suggested here are applicable to both relativistic and nonrelatitistic calculations.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560180415
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  • 6
    Electronic Resource
    Electronic Resource
    The use of scaled orbital functions in self-consistent field calculations for atoms (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 359-368 
    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: If a set of orbital functions φi(r) is an approximate solution to the self-consistent field equations for an atom, the scaled orbital functions ψi(r) = λi3/2φi(λir) will be a better solution if the scale parameters λi are properly chosen. The best choice of the scale parameters is determined by the variational principle. Two applications of this idea are made in this paper: one is an improved iteration scheme for solving the self-consistent field equations; the other is the calculation of the effects of relaxation when an electron is moved from one shell of an atom to another or is removed from the atom. In the first application the number of iterations required to converge the self-consistent field process is reduced by about two-thirds over the usual methods. In the second application, a sample calculation for argon shows the relaxation energies on ionization being calculated to within 0.5 eV.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260833
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  • 7
    Electronic Resource
    Electronic Resource
    Collisional time-correlation functions for molecular interactionsThis work was partly supported by National Science Foundation Grant No. CHE83-15696. (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 30 (1986), S. 773-785 
    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: Collisional time-correlation functions (TCFS) combine methods of scattering theory and of many-body theory to describe the interaction of projectiles with complex targets. In recent work, we have developed the theory of collisional TCFS for molecular interactions using multiple scattering expansions, semiclassical approximations and operator algebras. The theory has been applied to atomic collisions with molecules, to calculate cross sections and compare them with experiment.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560300769
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  • 8
    Electronic Resource
    Electronic Resource
    Variationally improved transition amplitudes from time-dependent Hartree-Fock wave functions: Application to He + He2+ collisionsWork partly supported by National Science Foundation grant No. CHE 83-15696. (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 30 (1986), S. 689-697 
    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: A variational functional is introduced to calculate transition amplitudes. It satisfies microscopic reversibility and is independent of the overall phases of the wave functions. Using time-dependent Hartree-Fock (TDHF) states, constructed from MO-LCAOS and evolving forward and backward in time, we compare exact numerical results with results from the variational functional for collisions of He and He2+, obtained with a minimal basis set. Transition probabilities versus impact parameters and cross sections versus collision energies in the range of 30-100 keV are computed for elastic and two-electron transfer processes. The variational functional method leads to a substantial improvement over the standard TDHF results.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560300761
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  • 9
    Electronic Resource
    Electronic Resource
    The theory of chemical reaction dynamics. Edited by D. C. Clary, D. Reidel Publishing Company, Dordrecht, Holland, 1986 (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 397-397 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320308
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  • 10
    Electronic Resource
    Electronic Resource
    Solvent stabilization of the edge inversion transition state in tetrahedral molecules (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 85-98 
    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 edge inversion process in phosphoric acid, PO(OH)3 has been studied by large scale ab initio molecular orbital theory. Edge inversion of the tetrahedral ground state via a square-planar transition state requires 69.5 kcal/mol (MP-2). Addition of two NH3 solvent molecules to the vacant NLUMO stabilizes the transition state by 45 kcal/mol (MP-2). The value for ΔH(300K) for the reaction 2NH3 + PO(OH)3 → PO(OH)3 · (NH3)2 is 24.1 kcal/mol (MP-2). The complex with two NH3 molecules is an intermediate. Addition of one NH3 to PO(OH)3 leads to an energy lowering of the planar form of 31 kcal/mol. This structure is now a transition state. The value for ΔH(300K) for the reaction NH3 + PO(OH)3 → PO(OH)3 · NH3 is 38.6 kcal/mol (MP-2). The complex of PF3O with two NH3 molecules was studied and is an intermediate. The value for ΔH(300K) for the reaction 2NH3 + POF3 → POF3 · (NH3)2 is only 3.3 kcal/mol (MP-2). Electron-donor solvents clearly will stabilize the edge inversion transition state for tetracoordinate main group compounds.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340814
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