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  • Atomic, Molecular and Optical Physics  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Generalized-molecular-orbital theory: Simple multiconfiguration self-consistent-field method (1978)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 14 (1978), S. 613-621 
    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: Even after completing a multiconfiguration self-consistent-field (MCSCF) calculation, one must often include additional configuration interaction (CI) to obtain quantitative or semiquantitative results. There is some question of whether the prior MCSCF calculation is worthwhile, if additional CI is needed later. We have developed a new MCSCF computational method, which, because of our assumptions about the nature of the configurations, yields one Fock-like operator for all the “filled” orbitals (high occupation numbers) and a second Fock-like operator for all the “virtual” orbitals (low occupation numbers). Since there are only two matrices to build, our method is considerably faster than other MCSCF approaches. Because of these similarities to standard molecular-orbital (MO) calculations, we have termed our approach generalized-molecular-orbital (GMO) theory. However, the “virtual” orbitals, unlike those of standard MO theory, are optimized to correlate the “filled” ones and can he used in a subsequent CI calculation. Results are presented for the correlation energy of H2O, the spectroscopic constants of N2, the singlet-triplet energy separations in CH2, and the nature of the chromium-chromium quadruple bond. Although these results are at a very low level of CI, the GMO approach appears to correct for the gross deficiencies of the single-determinant SCF procedure.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560140508
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  • 2
    Electronic Resource
    Electronic Resource
    Geometry optimization of organometallic complexes: A study of basis sets (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 503-512 
    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: Total geometry optimizations are reported for Cr(CO)6, HMn(CO)5, Fe(CO)5, Ni(CO)4, Cr(C6H6)2, Fe(C5H5)2, Ni(C4H4)2, Cr(NO)4, (C5H5)Mn(CO)3, and (C6H6)Cr(CO)3. A variety of basis sets were examined, and, based on the results, a relatively compact and accurate basis set is proposed. The differences between the calculated and experimental metal-carbonyl, metal-benzene, and metal-nitrosyl bond distances average 0.03, 0.08, and 0.07 Å, respectively. Calculated metal-cyclopentadienyl bond lengths were found to be an average of 0.15 Å longer than experimental bond lengths. Addition of electron correlation at the perfect pairing GVB level reduced the average difference in the metal-cyclopentadienyl bond length to 0.08 Å.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320749
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