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  • Computational Chemistry and Molecular Modeling  (10)
  • Wiley-Blackwell  (10)
  • Wiley
  • 1
    Electronic Resource
    Electronic Resource
    Two-parameter ω-technique for MO calculations (1977)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 11 (1977), S. 759-766 
    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 two-parameter ω-technique for MO calculations is proposed. The parameters ω and ω′ are chosen empirically to obtain a good agreement between calculated and observed bond lengths. The method amounts to an inclusion of the effect of nearest-neighbour electronic repulsion integrals into the conventional ω-technique.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560110508
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  • 2
    Electronic Resource
    Electronic Resource
    A study of some potential energy functions for diatomic molecules (1970)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 4 (1970), S. 579-586 
    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 detailed study of the performance of the Morse, the Hulburt--Hirschfelder and the Lippincott potential energy functions has been carried out by comparing them with the Rydberg-Klein-Rees potential energy curves for a number of electronic states of various diatomic molecules. Further, by employing the above potential energy functions, the radial Schrödinger equation has been solved for the vibrational energy levels, G(v), and the vibrational wave functions, ψv. The latter have been employed to determine the rotational constants, Bv, for the individual vibrational energy levels. Then the molecular constants, we, wexe, weye, Be, αe and γe for the various electronic states, have been computed by using the values of G(v) and Bv. A comparison of the molecular constants derived in this manner with the experimental ones reveals better agreement, in most cases, than that reported by previous workers.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560040605
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  • 3
    Electronic Resource
    Electronic Resource
    Calculation of excited-state properties of some small molecules: Comparative study of the CNDO/S and CNDO/2-vn-1 potential methods (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1695-1705 
    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 transition energy and geometry of the lowest excited (nπ*) singlet and triplet states of CO, CS, HNO, H2CO, HFCO, and F2CO molecules are calculated by CNDO/S and CNDO/2-VN-1 potential methods, and the results are compared with those of experimental and ab initio theoretical studies, wherever available. In the calculation of the vertical transition energy, the performance of the CNDO/S method is seen to be generally more satisfactory than that of the CNDO/2-VN-1 potential method, while the reverse is true for the excited-state geometry. The CNDO/S method as such fails to describe the geometry of the excited state, but a combined version (CNDO/S-2) of CNDO/S and CNDO/2, as well as the CNDO/2-VN-1 potential method is fairly successful in this regard.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560230502
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  • 4
    Electronic Resource
    Electronic Resource
    Automatic geometry optimization for molecules with d orbitals. III. The EHT method with electrostatic correctionsPart II: see Ref. 1. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 585-591 
    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 procedure has been developed for automatic optimization of molecular structures in the EHT method with possible inclusion of electrostatic correction terms, operating with analytical formulas for the first derivative of the total energy in Cartesian coordinates in the s, p, d basis of Slater orbitals. Illustrative examples are given of optimization of the structural parameters of FeCl3, Fe2Cl6, FeCl4, FeCl4-, FeCl2, and FeCl2+ and of optimization of the reaction pathways of the dissociation of Fe2Cl6 yielding the other species of the above set. The values are in good argreement with the available experimental data; this agreement is discussed briefly in connection with the general applicability of the EHT method combined with automatic geometry optimization to theoretical study of compounds containing transition metal atoms.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190412
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  • 5
    Electronic Resource
    Electronic Resource
    Transition probabilities for the ionization of N2, O2, NO and CO moleculesThis work was sponsored by the National Aeronautics and Space Administration, Washington, D.C., 20546, and the Air Pollution Division of Bureau of State Services, Public Health Service, Bethesda, Maryland, U.S.A.This computation was carried out on the IBM 360-75 computer at the Institute for Space Studies, 2880 Broadway, New York, New York and the IBM 7094 computer at the Goddard Space Flight Center, Greenbelt, Maryland, U.S.A. (1968)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 2 (1968), S. 325-332 
    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
    Description / Table of Contents: On a calculé des facteurs de Franck-Condon pour les molécules N2, O2, NO et CO pour les transitions aux états ionisés observés. Les calculs ont été basés sur les courbes de potentiel de Rydberg-Klein-Rees (RKR) des états électroniques en question. On a observé que pour certaines transitions, les facteurs de Franck-Condon basés sur les courbes de potentiel RKR diffèrent d'une façon appréciable de ceux obtenus de la fonction de potentiel de Morse. L'effet d'une substitution isotopique sur les probabilités de transition est aussi significatif dans plusieurs cas.
    Abstract: Franck-Condon-Faktoren wurden für die Moleküle N2, O2, NO und CO für Übergänge zu den beobachteten ionisierten Zuständen mit den Rydberg-Klein-Rees (RKR) Potential-kurven der entsprechenden elektronischen Zustände berechnet. Es wurde bemerkt dass für gewisse Übergänge die Franck-Condon-Faktoren der RKR Potentialkurven merkbar von den der Morse-Potentialfunktion abweichen. Der effekt isotopischer Substitution auf den Übergangswahrscheinlichkeiten ist auch in vielen Fallen ganz bedeutsam.
    Notes: Franck-Condon factors are presented for the normal and stable isotope-labelled N2, O2, NO and CO molecules for transitions to the observed ionized states by using the Rydberg-Klein-Rees (RKR) potential energy curves of the various electronic states involved. It has been observed that for some transitions, the Franck-Condon factors based on the RKR potential energy curves differ appreciably from those based on the Morse potential function. The effect of isotopic substitution on the transition probabilities is also quite significant in a number of cases.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560020302
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of semi-empirical parameters on the simple random-phase approximation calculations of conjugated hydrocarbons (1977)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 12 (1977), S. 639-654 
    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: Singlet-singlet transition energies, oscillator strengths, triplet energy levels, and the ground state correlation energy of a number of conjugated hydrocarbons have been calculated by the simple random-phase approximation (RPA) within the framework of the Pariser-Parr-Pople (PPP) model. The effect of semi-empirical parameters in such calculations has been examined in detail. A set of parameters has been deduced from these parametric studies which is found to yield results for the singlet spectra of the molecules in excellent agreement with experiment. It is, however, not possible to treat the triplet states using these same parameters, since they produce triplet instabilities in all the molecules. The triplet instability problem associated with semi-empirical RPA calculations has been discussed in detail.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560120405
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  • 7
    Electronic Resource
    Electronic Resource
    Automatic geometry optimization for molecules with d orbitals. I. General analytic formulas for derivatives of slater orbitals (1978)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 13 (1978), S. 227-233 
    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: General analytic formulas for derivatives of real Slater orbitals with respect to the Cartesian coordinates x and y have been derived. The application of this result to molecular geometry optimization or to the construction of a force constant matrix is briefly discussed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560130208
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  • 8
    Electronic Resource
    Electronic Resource
    Density functional theory including Van Der Waals forces (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 247-255 
    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 progress report is given of an extension of the density functional formalism to include long-range interactions such as van der Waals or dispersion forces. This is done by proving a general expression for the so-called exchange-correlation energy to contain and to describe such interactions just as well as any other treatment. The proper long-range forms of the interactions are derived explicitly in the cases of two neutral atoms, an atom outside a metal surface, and two parallel metal surfaces. The long-standing problem of treating the attractive and repulsive forces on the same footing in this way gets a solution. For practical calculations, an approximate form, based on an analysis in the weakly inhomogeneous limit and on a limiting form of the three-point function given by Rapcewicz and Ashcroft, is proposed and applied to some prototype cases. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560560410
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  • 9
    Electronic Resource
    Electronic Resource
    Critical comparison of the ab initio and spectroscopic methyl-C—H bond length difference in acetyl compounds, CH3C(=O) XArticle no. 35 in the series Ab Initio Studies of Structural Features Not Easily Amenable to Experiment. (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 517-522 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: In order to provide additional data for the relative lengths of methyl-C—H bond distances in acetyl derivatives, which are difficult to determine accurately by the conventional tools of structural chemistry, the geometries of CH3COH, CH3COF, CH3COCH3, CH3COOH, and CH3CONH2 were determined by ab initio SCF gradient optimization at the 5-31G** level and compared with previous 4-21G results. For acetaldehyde 6-311G4* calculations were also performed and the correlated methyl-C—H stretching potential energy functions were determined. It is found that the calculated differences between the in-plane and out-of-plane methyl-C—H bonds are practically independent of the computational scheme. The calculated results are in contrast to relative bond lengths obtained by some vibrational overtone spectroscopic studies, but are in perfect agreement with C—H bond length differences determined from isolated C—H stretching frequencies of partially deuterated compounds. The reliability of the latter, and other spectroscopic data concerning the assignment of the methyl-C—H vibrations are critically analyzed. On the basis of the available evidence we conclude: (1) the methyl groups of the CH3C(=O)X systems here discussed contain one strong (in-plane) and two weak (out-of-plane) C—H bonds; (2) intensities of C—H local mode spectra do not provide a reliable basis for assignment to individual bonds.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540050603
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  • 10
    Electronic Resource
    Electronic Resource
    Generating wave functions from classical trajectory calculations: The divergence of streamlines (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 239-244 
    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: Wave functions can be written, for short de Broglie wavelengths, in an eikonal form where the preexponential factor relates to the divergence of streamlines. A method is presented to calculate this divergence by generating the Jacobian of a variable transformation along a classical trajectory without requiring the simultaneous integration of adjacent trajectories. For a system with N + 1 degrees of freedom, there are 2(N + 1)2 differential equations that must be solved simultaneously to generate the trajectories and the Jacobian. Results are presented for a photodissociation cross section calculation in which the eikonal wave functions have been used in the transition integrals.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320726
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