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  • 1
    Electronic Resource
    Electronic Resource
    The ab initio calculation of inner sphere reorganization energies of inorganic redox couples (1993)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 115 (1993), S. 2898-2902 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00060a043
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  • 2
    Electronic Resource
    Electronic Resource
    A CI study of the CuCO and CuCO+ complexes (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 1690-1700 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: MO CI calculations are carried out using an optimal space of valence virtual MOs obtained by means of a projection technique, as a linear combination of the AOs which are more occupied in the molecular Fock space. Localization of the occupied MOs and nonvalence virtual MOs is also achieved. The overall procedure is proven to be quite advantageous and well suited to obtain potential energy curves which keep the same physical meaning along the range of distances studied. Using a slightly better than double-zeta quality basis set, a valence CAS-CI, and selected CI wave function by the CIPSI algorithm have revealed a possible weak van der Waals interaction for the 2Σ+ state of CuCO, which remains when polarization functions are added to the basis set for the carbon and oxygen atoms. Even though the CuCO 2Π and CuCO+ 1Σ+ states are energetically close, the nature of the interactions is quite different, π bonding and mainly electrostatic, respectively. The results give further support to the view of the neutral metal–CO interaction as a balance of σ repulsion and π backbonding. However, it is proposed that the driving force for the positive ion metal–CO interaction becomes essentially electrostatic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453234
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  • 3
    Electronic Resource
    Electronic Resource
    Ab initio study on the low-lying excited states of retinal (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 1112-1122 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio results for the electronic spectrum of all-trans-retinal and its truncated model 3-methyl-all-trans (10-s-cis)-2,4,6,8,10-undecapentaen-1-al are presented. The study includes geometry determination of the ground state. Vertical excitation energies have been computed using multiconfigurational second-order perturbation theory through the CASPT2 formalism. The lowest singlet excited state in gas phase is predicted to be of nπ* character. The lowest triplet state corresponds, however, to a ππ* state. The most intense feature of the spectrum is due to the strongly dipole-allowed ππ* transition, in accordance with the observed maximum in the one-photon spectra. The vertical excitation energies of the Bu- and Ag-like states are found close, the latter (approximate)1 eV higher than the maximum in the two-photon spectra. Solvent effects and nonvertical nature of the observed maximum in the two-photon spectra are invoked in rationalizing the deviation with respect to the best present estimate for the Ag-like state. In addition, qualitative aspects of the one-bond photoisomerization about the C11=C12 double bond of retinal are considered. The overall isomerization picture from 11-cis into all-trans-retinal, as taking place mainly along the triplet manifold, agrees with experimental evidence.© 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473207
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  • 4
    Electronic Resource
    Electronic Resource
    On the theoretical determination of the electron affinity of ozone (1993)
    Springer
    Theoretical chemistry accounts 86 (1993), S. 467-476 
    Details
    ISSN: 1432-2234
    Keywords: Ozone ; Electron affinity ; CAS ; SCF
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Multiconfigurational electron correlation methods have been analyzed in order to theoretically compute the electron affinity (EA) of ozone. The near-degeneracy correlation effects, which are so important in O3 and O 3 − , have been described using complete active space (CAS) SCF wave functions. Remaining dynamic correlation effects are computed using second-order perturbation theory (the CASPT2 method). The best calculated adiabatic value (including zero-point energy corrections), 2.19 eV, is about 0.09 eV larger than the experimental value. Comparative studies using size-consistent coupled pair functional approaches (CPF and ACPF) have also been performed. The harmonic frequencies in O 3 − have been determined to be: ω1=992, ω2=572, and ω3=879 cm−1, which gives a zero-point energy of 0.151 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113945
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  • 5
    Electronic Resource
    Electronic Resource
    A theoretical determination of the electronic spectrum of Methylenecyclopropene (1996)
    Springer
    Theoretical chemistry accounts 94 (1996), S. 143-154 
    Details
    ISSN: 1432-2234
    Keywords: Electronic spectrum ; Methylene cyclopropene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The vertical electronic spectrum of methylenecyclopropene, the prototype of the nonalternant hydrocarbons known as fulvenes, has been studied using multiconfigurational second-order perturbation theory. The calculations comprise three valence states and the 3s, 3p, and 3d members of the Rydberg series converging to the first π ionization limit. Vertical excitation energies to three valence states are found at 4.13, 6.12, and 6.82 eV. The second of them corresponds to an excitation from the highest occupied σ orbital to a π* orbital, while the other two are π → π* excitations. The third transition gives rise to the most intense feature in the electronic spectrum. The results are rationalized within the scheme of two interacting double bonds. Comparisons are made between this and the previous theoretical calculations of the electronic spectra of related systems and also between the available experimental data of methylenecyclopropene in solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191645
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  • 6
    Electronic Resource
    Electronic Resource
    A theoretical determination of the dissociation energy of the nitric oxide dimer (1994)
    Springer
    Theoretical chemistry accounts 88 (1994), S. 425-435 
    Details
    ISSN: 1432-2234
    Keywords: Nitric oxide dimer ; Dissociation energy ; Structure, ACPF Method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Multi-reference CI methods have been applied to determine the dissociation energy and structure of thecis-N2O2 molecule. The convergence of the theoretical result has been checked with respect to a systematic expansion of the one-electron basis set and the multi-reference CI wave function. The best calculated value, 13.8 kJ/mol, is in agreement with the experimental value, 12.2 kJ/mol. It has been obtained with an extended ANO-type basis set [6s5p3d2f], including the effect of the basis set superposition error (BSSE) in the geometry optimization, and additional effects, such as the electron correlation of core electrons and relativistic corrections, using the average coupled pair functional (ACPF) approach. The optimal geometry computed at this level was found to be:r(NN)=2.284 Å,r(NO)=1.149 Å, and 〈NNO=96.1°. Employing the [6s5p3d2f] basis set, the BSSE was found to be ≈2 kJ/mol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113292
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  • 7
    Electronic Resource
    Electronic Resource
    An ab initio CI study on the rotational barrier of the allyl anion (1986)
    Springer
    Theoretical chemistry accounts 69 (1986), S. 101-106 
    Details
    ISSN: 1432-2234
    Keywords: Rotational barrier ; Allyl anion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract All-electron and pseudopotential non-empirical calculations have been performed on C 2v and C s (syn, anti) allyl anion conformations. Using a double-zeta valence-shell basis set within the Epstein-Nesbet definition of the unperturbed Hamiltonian, a value about 19 kcal/mol is found for the barrier to rotation of the allyl anion. This value is the theoretical value obtained with greater accuracy, and the lowest one for the rotational barrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527682
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  • 8
    Electronic Resource
    Electronic Resource
    A theoretical determination of the electronic spectrum of Methylenecyclopropene (1996)
    Springer
    Theoretica chimica acta 94 (1996), S. 143-154 
    Details
    ISSN: 0040-5744
    Keywords: Key words: Electronic spectrum ; Methylene cyclopropene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract.  The vertical electronic spectrum of methylenecyclopropene, the prototype of the nonalternant hydrocarbons known as fulvenes, has been studied using multiconfigurational second-order perturbation theory. The calculations comprise three valence states and the 3s, 3p,  and 3d members of the Rydberg series converging to the first π ionization limit. Vertical excitation energies to three valence states are found at 4.13, 6.12, and 6.82 eV. The second of them corresponds to an excitation from the highest occupied σ orbital to a π* orbital, while the other two are π→π* excitations. The third transition gives rise to the most intense feature in the electronic spectrum. The results are rationalized within the scheme of two interacting double bonds. Comparisons are made between this and the previous theoretical calculations of the electronic spectra of related systems and also between the available experimental data of methylenecyclopropene in solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191645
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    Paper (German National Licenses)
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