Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1990-1994  (10)
Source
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Theoretical investigations of terminal alkenes as putative suicide substrates of cytochrome P-450 (1990)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 112 (1990), S. 8686-8691 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00180a008
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    On the dissociation energy of Mg2 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5377-5383 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The bonding in the X 1Σ+g state of Mg2 is investigated using near-complete valence one-particle Slater and Gaussian basis sets containing up to h functions. Full configuration interaction (FCI) calculations are used to calibrate four-electron correlation treatments. We show that the four-electron complete CI limit can be approached using a sequence of either second-order CI (SOCI) or interacting correlated fragment (ICF) calculations. At the valence level, our best estimate of the dissociation energy (De) is 464 cm−1. We show that this is a lower limit and probably within 5 cm−1 of the complete basis value. The inclusion of core–valence correlation using a model operator approach decreases De by about 35 cm−1 and increases the bond length by 0.03 a0, thereby yielding spectroscopic constants in good agreement with experiment. Attempts to compute the core–valence effect accurately by expanding the CI treatment were unsuccessful.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458515
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Calculations of H2O microwave line broadening in collisions with He atoms: Sensitivity to potential energy surfaces (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1346-1359 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Broadening parameters for three microwave lines of water at 22.2, 183.3, and 380.2 GHz, in a bath of helium atoms, are calculated using accurate molecular scattering S matrices obtained from two theoretical potentials presented by Palma et al., J. Chem. Phys. 89, 1401 (1988). For the 22 GHz line results are in substantial agreement with values presented in that work, indicating the accuracy of approximate methods used there. The present work improves the potential energy surfaces, computed from perturbation theory (MP4) and variational interacting correlated fragments (ICF1) wave funcitons, by correcting them for basis set superposition error (BSSE), and recomputes the line broadening using a different procedure for fitting computed energy points. In addition, the entire set of calculations are repeated with a quite different basis set for orbital expansion to establish the reliability of the potential energy surface. We show that adjustments for superposition error are essential, and that broadening cross sections computed from the new surfaces are changed 10%–30% from the old, significantly improving agreement with experiment. The MP4 BSSE adjusted surface appears to be the most accurate, giving room temperature broadenings of 8.9, 11.8, and 10.0 A(ring)2 compared with experimental determinations of 12.2±1.2 , 11.9, and 11.2 A(ring)2 for the 22, 183, and 380 GHz lines, respectively. Thus, computed line to line variation is larger than observed. The ICF1 BSSE adjusted results for pressure broadening cross section parallel those from the MP4 BSSE calculations but are about 10% smaller. We believe our computed results are stable with respect to basis set for orbital expansion and that the scattering calculations are accurate. Any theoretical inadequacy has been pinpointed to too few points on the potential energy surface resulting in an inadequate description of the angle dependence. It is not clear whether the present discrepancy between computation and experiment stems from this or from errors in the experimental values, although we show some indication that additional information on the surface might decrease the computed broadenings, worsening agreement with experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459992
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Calculations on the rate of the ion–molecule reaction between NH+3 and H2 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7842-7849 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rate coefficient for the ion–molecule reaction NH+3 +H2→NH+4+H has been calculated as a function of temperature with the use of the statistical phase space approach. The potential surface and reaction complex and transition state parameters used in the calculation have been taken from ab initio quantum chemical calculations. The calculated rate coefficient has been found to mimic the unusual temperature dependence measured in the laboratory, in which the rate coefficient decreases with decreasing temperature until 50–100 K and then increases at still lower temperatures. Quantitative agreement between experimental and theoretical rate coefficients is satisfactory given the uncertainties in the ab initio results and in the dynamics calculations. The rate coefficient for the unusual three-body process NH+3+H2+He→NH+4+H+He has also been calculated as a function of temperature and the result found to agree well with a previous laboratory determination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460119
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Anisotropic rigid rotor potential energy function for H2O–H2 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 5824-5830 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have calculated the interaction for H2O–H2 at 722 points on a five-dimensional surface where both molecules are treated as rigid rotators and we have fitted the ab initio points to a 48-term angular expansion of products of spherical harmonics and rotation matrices. The resulting potential energy function shows strong angle dependence with a large contribution from electrostatic interactions. When averaged over H2 orientations, the resulting water-atom-like surface is found to have zero crossing and minimum at similar distances to the corresponding H2O–He surface but to be generally more repulsive at short range and more attractive at long range. The isotropic average of the potential has a zero-crossing radius σ=3.05 A(ring) and a well depth ε=49.5 cm−1 at an intermolecular separation Rm=3.52 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467297
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Theoretical calculations and experimental studies on the electronic structures of hydrazones and hydrazone radical cations: formaldehyde hydrazone and benzaldehyde diphenylhydrazones (1990)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 94 (1990), S. 90-98 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100364a014
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Calculations on the competition between association and reaction for C3H++H2 (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 2812-2820 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A potential energy surface has been calculated for the competing associative and reactive ion–molecule processes involving the reactants C3H++H2. Our ab initio results show that the linear ion C3H+ and H2 can directly access the deep potential well of the propargyl ion H2CCCH+, which is calculated to lie 390 kJ mol−1 below the zero-point energy of the reactants. Isomerization between the propargyl ion and the lower energy, cyclic C3H3+ ion, calculated to lie 501 kJ mol−1 below the zero-point energy of reactants, can subsequently occur via two pathways. One of these pathways involves a transition state lying 22 kJ mol−1 below the energy of the reactants while the other, which occurs at much lower energies, involves two transition states and an intermediate. The dissociation of c-C3H3+ into c-C3H2++H is calculated to occur directly, without any intermediate potential energy maximum, but the energy of the products lies 7.3 kJ mol−1 above the energy of the reactants. Using the minimum energy potential pathway and properties of the stationary point structures determined via ab initio methods, we have calculated both the association rate coefficient to produce C3H3+ as a function of density and the branching ratio between the propargyl and cyclic structures of the ion. Our results are in good agreement with some experimental results and in conflict with others. Specifically, we agree with the 1:1 branching ratio measured for the propargyl and cyclic isomers of C3H3+ at 80 and 300 K and we agree with the rate coefficient for radiative association measured at 80 K. We cannot reproduce reported measurements that the reactive channel (C3H2++H) is the dominant channel at 80 K and at low gas densities, or that the association channel at high densities saturates at an effective rate coefficient well below the Langevin value −2×10−11 cm3 s−1 at 300 K and 1×10−10 cm3 s−1 at 80 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465190
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Comment on broadening of water microwave lines by collisions with helium atoms (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8150-8156 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Earlier theoretical descriptions of interaction forces and collision dynamics in the H2O–He system [A. Palma et al., J. Chem. Phys. 89, 1401 (1988); S. Green et al., ibid. 94, 1346 (1991)] are improved by calculating the interaction at additional orientations and by including diffuse functions in the molecular orbital expansion basis set. The improvements make substantial changes to the potential energy surface, but make only small changes in predicted microwave pressure broadening coefficients. The qualitative temperature dependence and relative widths of different lines appear to be converged with respect to successive improvements to the theoretical description of this system. Remaining discrepancies with available data must reflect problems with the experimental values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462318
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    The potential energy curves of the X 1Σg+ ground states of Mg2 and Ca2 using the interacting correlated fragments model (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 8424-8431 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report ground-state potential energy curves for Mg2 and Ca2 calculated in a large Slater-type basis using the interacting correlated fragments (ICF) model of Liu and McLean. Within the framework of the model, we study convergence of the potential curves with respect to the amount of intrafragment electron correlation introduced into each of the interacting atoms. The ICF model requires localized orbitals and the convergence rate can be affected dramatically by the localization choice; we illustrate and discuss this effect. Successful application of the ICF model requires careful treatment of the basis set superposition error and we discuss this. Our best calculations with four electrons correlated in Mg2 give De=458.8 cm−1 compared with an estimated lower limit for the four correlated electron calculation of 464 cm−1 and an experimental value of 429.6 cm−1. The bulk of the difference between calculation and experiment is attributed to intrafragment core–valence correlation effects which decrease the dissociation energy by nearly 30 cm−1. In parallel calculations on Ca2, our computed four correlated electron De is 1236 cm−1 compared to the experimental 1095.4 cm−1, showing that core–valence electron correlations are responsible for decreasing the dissociation energy by approximately 149 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463412
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Computed self-consistent field and singles and doubles configuration interaction spectroscopic data and dissociation energies for the diatomics B2, C2, N2, O2, F2, CN, CP, CS, PN, SiC, SiN, SiO, SiP, and their ions (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 8459-8464 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Single configuration self-consistent field (SCF) calculations near the Hartree–Fock limit, and singles and doubles configuration-interaction (CI)(SDCI) calculations from this single SCF configuration have been performed for the ground and selected excited states of the molecules B2+, B2, C2+, C2, N2+, N2, O2+, O2, F2+, F2, CN, CN−, CP, CS, PN, SiC, SiC−, SiN, SiN−, SiO, and SiP. Potential energy curves, with Davidson corrections, have been obtained around equilibrium separations. Equilibrium bond lengths, vibrational energies, ionization potentials, and dissociation energies are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463417
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...