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  • 1
    Electronic Resource
    Electronic Resource
    Ring opening of cyclopropylidenes to allenes: reactions with bifurcating transition regions, free internal motions, steric hindrances, and long-range dipolar interactions (1986)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 108 (1986), S. 3147-3149 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00271a078
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Potential energy surfaces of ozone. I (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 8054-8069 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The cross section through the ground-state potential energy surface of ozone which contains the open minimum, the ring minimum, and the ring-opening reaction path, including the ring-opening transition state, is determined through full-valence-space multiconfiguration self-consistent-field calculations. It is shown that, at a point on the ridge separating the open-structure basin from the ring-structure basin in C2v symmetry, very close to the transition state, the ground-state surface connects with the lowest excited state surface of the same symmetry (1A1). This point is part of an intersection seam between these two 1A' surfaces in Cs symmetry. It is furthermore found that the upper state has its equilibrium structure very close to the transition state of the lower state. The quantitative data of all critical points are calculated. In addition, a ground-state potential energy surface cross section describing the detachment of an oxygen atom is determined. For several other states, C2v constrained and bond-length-optimized energy curves E(φ) are also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460140
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  • 3
    Electronic Resource
    Electronic Resource
    Extracting more than a few eigenvectors from a dense real symmetric matrix: Optimal algorithms versus the architectural constraints of the FPS-X64 (1987)
    Springer
    Theoretical chemistry accounts 71 (1987), S. 169-186 
    Details
    ISSN: 1432-2234
    Keywords: Diagonalization ; eigenvector ; Inverse ; Iteration ; Householder ; Givens, EISPACK ; HQRII
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ten widely available sets of routines, including HQRII, QCPE GIVENS and EISPACK 3, were evaluated for reliability, robustness, accuracy, speed, compactness, portability and simplicity. All were found lacking in one or more areas. Modified versions of the EISPACK routines TRED3, TQLRAT, TINVIT and TRBAK3 performed somewhat better. Changes to TINVIT were especially important for improved speed, accuracy and reliability. To achieve the maximum capabilities of the FPS-X64 series of computers access to table memory is required, but since the FORTRAN compiler does not allow this and there is no library support for the required operations, it was necessary to write three routines in APAL. The standard algorithm needs to be modified before full efficiency can be achieved for the back transformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00526415
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  • 4
    Electronic Resource
    Electronic Resource
    Chemical binding and electron correlation in diatomic molecules as described by the FORS model and the FORS-IACC model (1985)
    Springer
    Theoretical chemistry accounts 68 (1985), S. 69-86 
    Details
    ISSN: 1432-2234
    Keywords: Electron correlation ; Atoms in molecules ; FORS/CASSGF ; Diatomic molecules ; Dissociation curves ; Spectra ; Dipole moments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using the model of the Full Optimized Reaction Space including the Intra-Atomic Correlation Correction, binding energies and other electronic properties have been calculated for several states of a number of diatomic molecules. In most cases this theoretical approach yields results agreeing with experimental values to within 0.2 eV. The investigation covers the molecules BH, CH, NH, OH, FH, N2, O2, F2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00698752
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  • 5
    Electronic Resource
    Electronic Resource
    Generation of a full active configuration space basis in terms of symmetry- and spin-adapted antisymmetrized orbital products (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 489-505 
    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 practical algorithm is described for generating a set of symmetry- and spin-adapted antisymmetrized products of molecular orbitals (SAAPs) which form an orthogonal basis for a full active configuration space. The spin-adaptation is completely general. The space-symmetry adaptation is accomplished for the groups C∞v and D∞v.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560310320
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  • 6
    Electronic Resource
    Electronic Resource
    A configuration interaction study of the spin dipole-dipole parameters for formaldehyde and methylene (1973)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 7 (1973), S. 999-1019 
    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 electron spin dipole-dipole contribution to the zero field splitting has been evaluated for the 3A2 (n → π*) and 3A1 (π → π*) states of formaldehyde using a CI wave function constructed from contracted Gaussian-lobe functions. The values D = 0.539 cm-1 and E = 0.031 cm-1 were obtained for the 3A2(n → π*) state and D = -0.588 cm-1 and E = 0.058 cm-1 were obtained for the 3A1 (π → π*) state using the CI wave function constructed from SCF orbitals of the respective parent configurations. An analysis of the effect of CI on the parameters is given for the 3A2 (n n → π*) state of formaldehyde and the 3B1 ground state of methylene. Numerical results are given which show that internally consistent self-consistent field orbitals (ICSCF) are superior to canonical SCF orbitals as a starting point for a CI calculation. Our CI wave function for the 1A1 ground state gave an energy of -114.13658 hartrees which is significantly lower than any previously reported energy calculation. This wave function gives a dipole moment of 2.22 Debye (C+O-) in good agreement with the experimental value of 2.33 ± 0.02 Debye.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560070515
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  • 7
    Electronic Resource
    Electronic Resource
    Ab initio calculations on urea (1974)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 8 (1974), S. 857-892 
    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: Multiconfiguration wave functions constructed from contracted Gaussian-lobe functions have been found for the ground and valence-excited states of urea. ICSCF molecular orbitals of the excited states were used as the parent configurations for the CI calculations except for the 1A1(π → π*) state. The 1A1(π → π*) state used as its parent configuration an orthogonal linear combination of natural orbitals obtained from the second root of a three-configuration SCF calculation. The lowest excited states are predicted to be the n π → π* and π → π* triplet states. The lowest singlet state is predicted to be the n π → π* state with an energy in good agreement with the one known UV band at 7.2 eV. The π → π* singlet state is predicted to be about 1.9 eV higher, contrary to several previous assignments which assumed the lowest band was a π → π* amide resonance band. The predicted ionization energy of 9.0 eV makes this and higher states autoionizing.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560080604
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