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
  • 1
    Electronic Resource
    Electronic Resource
    Near doubling of hydrogen-hydrogen bond length in the "stretched" osmium molecular hydrogen complex [Os(NH3)4OAc(.eta.2-H2)]+: a theoretical study (1993)
    s.l. : American Chemical Society
    Inorganic chemistry 32 (1993), S. 2230-2231 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00063a003
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Electron and energy transfer through bridged systems. 6. Molecular switches: the critical field in electric field activated bistable molecules (1990)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 112 (1990), S. 4192-4197 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00167a014
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Prediction and experimental comparison of deuterium quadrupole coupling constants in some bifluoride salts: An extreme example of symmetric hydrogen bonding in different crystalline environments (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 2526-2539 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electric field gradient (EFG) at the deuterium nucleus of the bifluoride ion, a linear symmetrically H-bonded system, has been calculated using ab initio Hartree–Fock SCF, singles and doubles CI, and coupled pair functional methods using basis sets ranging from double zeta to the [7,5,2,1;5,4,2] contracted Gaussian set. For the free DF−2 ion, the EFG and the resulting nuclear quadrupole coupling constant (nqcc) are found to be very low and positive in sign, and to display marked dependences on basis set, and the effects of electron correlation and vibrational averaging. In particular, we note a peculiarly extreme basis-set limit problem for deuterium EFGs in symmetric H-bonded molecules. The effects of the crystal lattice on the nqcc have been calculated for the sodium, potassium, and ammonium bifluorides taking into account: the direct contribution of the lattice to the EFG as modeled by a point-charge distribution; its polarizing effect on an individual DF−2 ion using two different methods; and also the effects of librational averaging. The predicted deuterium nqccs and asymmetry parameters (η) in the bifluoride salts are compared with the free-ion values (η necessarily zero). While our predicted nqcc in KDF2 of 55±3 kHz is consistent with the only reported experimental value of 58±10 kHz [R. Blinc et al., Chem. Phys. Lett. 48, 596 (1977)], the calculated η value of 0.07±0.01 is at serious variance with the experimental value of 0.4±0.1. As our treatment of the crystal lattice effects is quite comprehensive this disagreement requires further investigation. We have predicted a significantly higher nqcc for NaDF2 of 83±3 kHz, but, again, with a very small η value of 0.04±0.01.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454031
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    An ab initio quantum chemical study of the hydrogen- and "anti''-hydrogen-bonded HF/ClF and HF/Cl2 dimers (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 535-544 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio electronic structure calculations at the SCF and coupled pair functional (CPF) level have been carried out for the hydrogen- and "anti''-hydrogen-bonded isomers of the ClF/HF and Cl2/HF complexes. The stability of each isomer with respect to its constituent monomers has been calculated at the appropriate optimized geometry, paying particular attention to correlation effects, zero point energies, and basis set superposition errors. The differences between the latter quantities for a given pair of isomers, all calculated to be (approximately-less-than)0.5 kcal mol−1, are comparable in magnitude to the difference in stabilities, hence in a quantitative description of bonding in these dimers all these effects must be considered. The dipole moments and the 35Cl and 2H nuclear quadrupole coupling constants for the dimers have also been evaluated and compared with the available experimental data. In agreement with the results of recent molecular beam measurements, in both systems the anti-hydrogen-bonded isomers are found to be the more stable ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453601
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    The analytic configuration interaction gradient method: The calculation of one electron properties (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 5976-5986 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The implementation of the analytical energy gradient method for the calculation of first order one electron properties using closed shell configuration interaction wave functions of the single reference plus single and double substitutions (CI-SD) type is discussed. The method used is based on the Z vector formalism of Handy and Schaefer which is readily extended to allow a full orbital optimization to be carried out for a given CI-SD wave function. The results of comparative test calculations are reported for the HF, H2O, CO, HCN, and O3 molecules, for which the dipole and quadrupole moments and the electric field gradients at the nuclei have been calculated by both the expectation value and the energy derivative formalisms using several standard basis sets. The effects of orbital optimization on the above properties at the equilibrium geometries as well as at a range of distorted geometries for HF, are also discussed. It is found that agreement between the different formalisms is best when the reference state in the CI expansion is strongly dominant. The DIIS scheme of Pulay has been incorporated into the orbital optimization method and has been found to be efficient in generating the fully optimized CI-SD/MCSCF wave functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453521
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Ab initio quantum chemical study of the molecular and spectroscopic (infrared and Raman) properties of sulfur dioxide: Comparison with ozone (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5721-5730 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using ab initio SCF, singles and doubles configuration interaction (CI-SD), and coupled pair functional (CPF) techniques with basis sets of triple zeta plus two polarization functions quality, the following properties have been computed for sulfur dioxide at its equilibrium geometry: dipole and quadrupole moments, electric field gradients at the nuclei, static and frequency dependent dipole polarizability (at λ=5154 A(ring) and λ=6328 A(ring)), dipole and polarizability derivatives, infrared absorption intensities, and Raman scattering activities. The properties, when calculated at the correlated level of theory have been evaluated by the energy derivative (ED) as well as the expectation value (EV) formalism. The results of the CPF(ED) calculations are in good agreement with the available experimental data and on the basis of additional two-configurational MCSCF studies the use of single reference CI-SD and CPF wave functions is judged to be justified. The analogous calculations on ozone serve to highlight the considerable differences between the two molecules, inasmuch as due to the considerably larger degree of near-degeneracy in O3, properties that involve mixing of the lowest 1B2 excited state with the 1A1 ground state are predicted poorly at the SCF level as well as at the single reference CI-SD and CPF levels of theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455582
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The prediction of nuclear quadrupole moments from ab initio quantum chemical studies on small molecules. II. The electric field gradients at the 17O, 35Cl, and 2H nuclei in CO, NO+, OH−, H2O, CH2O, HCl, LiCl, and FCl (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 416-423 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electric field gradients (efg's) at the oxygen and hydrogen nuclei in CO,NO+, OH−, H2O, and CH2O, and at the chlorine, lithium, and hydrogen nuclei in HCl, LiCl, and FCl, calculated using ab initio quantum chemical methods, are reported. Using extended Gaussian basis sets, the efg's at the oxygen and chlorine nuclei were computed at the self-consistent field (SCF), singles and doubles configuration interaction [CI(SD)], and coupled pair functional (CPF) levels of theory as the expectation values of the efg operator and also as the energy derivatives of the appropriate perturbed Hamiltonian using the finite field method. The efg's at the hydrogen and lithium nuclei were computed as expectation values. Corrections due to zero point vibrational motions were also calculated. The effect of basis set incompleteness on the calculated efg's is discussed and, where possible, corrected for. The calculated efg's, together with the experimental nuclear quadrupole coupling constants, are used to estimate the 17O, 35Cl, and 2H nuclear quadrupole moments, and to test the quality of the correlated wave functions generated by the CI(SD) and CPF methods. The recommended values on the basis of the present calculations are −2.64±0.03, −8.2±0.2, and 0.278 fm2, respectively, for the 17O, 35Cl, and 2H nuclear quadrupole moments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453586
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Spectroscopic constants of the X˜(1A1), a˜(3B1), and A˜(1B1) states of CF2, CCl2, and CBr2 and heats of formation of selected halocarbenes: An ab initio quantum chemical study (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2227-2238 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The geometries, rotational constants, harmonic force constants and frequencies, dissociation and term energies of CF2, CCl2, and CBr2 in their respective X˜(1A1), a˜(3B1) and A˜(1B1) states, computed by complete active space self-consistent field (CASSCF), complete active space second-order purturbation (CASPT2), and coupled-cluster with single, double and perturbative triple excitations [CCSD(T)] methods and cc-pVTZ basis sets, are reported. For CCl2 and CBr2 the barriers to linearity are also characterized. The computed spectroscopic constants are in good agreement with the available experimental data. The atomization energies and hence heats of formation at 0 and 298 K of these molecules as well as of CHF, CHCl, and CFCl, all in their lowest singlet ground states were also computed by the CCSD(T) method utilizing basis sets ranging from cc-pVDZ to aug-cc-pVQZ, cc-pCVQZ and G3large, enabling the extrapolation of the energies to a complete basis set (CBS) limit and the inclusion of core–valence correlation (with the exception of CBr2). Scalar relativistic corrections, computed by CASPT2, were also taken into account. The final CBS results are ΔfH2980(CHF)=147±4 kJ mol−1, ΔfH2980(CHCl)=320±4 kJ mol−1, ΔfH2980(CFCl)=29±4 kJ mol−1, ΔfH2980(CCl2)=229±4 kJ mol−1, and ΔfH2980(CBr2)=337±8 kJ mol−1. The GAUSSIAN-3 (G3) heats of formation of these molecules are within 2 kJ mol−1 of the CBS values, representing significant improvement over the GAUSSIAN-2 predictions which differ from the CBS results by up to ∼10 kJ mol−1. Similarly, the G3 triplet/singlet energy separations are found to be in good agreement with those obtained at the CCSD(T)/cc-pVQZ level of theory including core–valence correlation corrections, as well as experiment. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481592
    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 effect of intermolecular interactions on the 2H and 17O quadrupole coupling constants in ice and liquid water (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 2002-2013 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using ab initio SCF molecular orbital techniques, the electric field gradients (efg's) at the oxygen and hydrogen nuclei were calculated for water clusters ranging from dimer to pentamer in an attempt to reproduce the shift in 17O and 2H nuclear quadrupole coupling constants (qcc's) that is observed on going from ice to vapor. For 2H, where the qcc shift is due mostly to the change in O–H bond length, excellent agreement with the experimental vapor → ice shift was obtained. For 17O, the change in the qcc is found to be mainly electronic in origin, effectively due to the polarization of the charge associated with the oxygen atom, and approximately 75% of the observed qcc shift was reproduced. On the basis of the calculations, estimates of the 17O and 2H qcc's in liquid water were made that are consistent with the values obtained from an analysis of the available NMR relaxation data, provided that librational motions are properly taken into account. We also present results of SCF calculations on water interacting with a Li+, Na+, or Cl− ion, indicating that the effect of a nearby ion on the 2H and 17O qcc's is similar to that produced by H bonding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448384
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    The electronic spectroscopy of jet-cooled difluorocarbene (CF2): The missing A˜-state stretching frequencies (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 4476-4483 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The A˜(1B1)←X˜(1A1) electronic transition of difluorocarbene (CF2) has been studied by laser-induced fluorescence spectroscopy in a supersonic free jet and by ab initio theoretical methods. The radical was formed by pyrolysis of C2F4 at ∼1000 °C with a heating chamber at the tip of the nozzle just prior to the gas expansion. Fairly complete rotational cooling, but incomplete vibrational cooling allowed the identification of several new hot band transitions. Ab initio calculations for the X˜(1A1), a˜(3B1), and A˜(1B1) electronic states were performed using the CASSCF method in conjunction with Dunning's cc-pVTZ basis set, as well as two smaller sets. The calculations allow us to distinguish between several possible assignments of the observed transitions, and hence determine the vibrational frequencies of the two previously unassigned A˜-state stretching frequencies: ν3′=1180±2 cm−1 and ν1′=1011±2 cm−1. The ordering of these modes is different from that in the ground state (ν1″(approximately-greater-than)ν3″) and mechanisms for the switching are discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470728
    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...