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
    On the performance of high-level correlated single-reference methods: The energy, dipole moment, and polarizability functions of BH (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7300-7305 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The performance of the fourth-order many-body perturbation theory (MBPT) and different coupled cluster (CC) methods in calculations of the potential energy and electric property functions has been investigated for the X 1Σ+ state of the BH molecule. In spite of the single reference approximation most of these methods are capable of correctly predicting the shape of the energy and property functions. Both the qualitative features of these functions and their numerical values are considerably improved on passing from the MBPT to the CC models. The stability with respect to the near degeneracy of the reference state has been found to increase in the same way. Excellent results are obtained from the CC calculations for the potential energy and electric properties of the BH molecule in the vicinity of the equilibrium bond distance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456208
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A theoretical study of the A 1Π←X 1Σ+ system of SiH+ (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 423-432 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Theoretical studies have been performed on the X 1Σ+ and A 1Π states of SiH+. The complete active space, self-consistent field (CASSCF) and many-body perturbation theory (MBPT) methods were employed for the X 1Σ+ and state while the A 1Π excited state potential energy curve was studied by using CASSCF, multireference contracted configuration interaction (MR CCI, (MR CEPA), and coupled pair functional (CPF) approaches. Excellent agreement was obtained with experiment for the X state spectroscopic parameters (CASSCF): re=1.505 (1.50 A(ring); D0=3.30 (3.22±0.03) eV; ωe=2161 (2155) cm−1; ΔG1/2=2093 (2089) cm−1, with experimental values within parentheses. The shape of the potential curve for the A state was very sensitive to the basis set and higher order electron correlation. The best results, obtained with the CPF method, were re=1.888 (1.871) A(ring); D0=0.15 (0.15±0.03) eV; ωe=438 (448) cm−1; ΔG1/2=318 (389) cm−1. The computed f0,0 oscillator strength for the A←X transition was 1.2×10−3 which falls between the laboratory value, (2.4±1)×10−3, and a value obtained from the solar spectrum, 0.5×10−3. The computed life time for the v'=0 state is 956 ns to be compared to the experimental value 1025±80 ns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455483
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Optimized virtual orbital space for high-level correlated calculations. II. Electric properties (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5749-5758 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The optimized virtual orbital space (OVOS) technique recently proposed for high-level correlated calculations of energy surfaces, is shown to be nearly as efficient for electric field properties. In particular, the polarizability of F−, and the dipole moment and polarizability of FH as a function of internuclear separation are studied. A reduction of the virtual space to about one-half has a negligible effect on the dipole moment and polarizabilities for FH and F− examples. A further reduction to one-quarter is reliable when augmented with the exact second-order result, obtained as a by-product of the OVOS generation. This enables the extension of high-level correlated methods to systems at least 2–4 times larger than those that could be accurately studied using the full space of virtual orbitals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454721
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Proton magnetic shielding in the water molecule (1972)
    Springer
    Theoretical chemistry accounts 27 (1972), S. 135-145 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die ungekoppelte Hartree-Fock Variationsstörungsrechnung von Karplus u. Kolker wird für die Berechnung von Eigenschaften 2. Ordnung des Wassermoleküls verwendet. Für die Berechnung wird die SCF MO SCGO-Wellenfunktion des Grundzustandes gewählt, und die gestörten Orbitale 1. Ordnung werden in der multiplikativen Form approximiert. Die Konvergenz der Methode und die Frage, ob die Eichinvarianz verletzt wird, werden untersucht. Für den gewählten Potential-Nullpunkt im Zentrum der negativen Ladungsverteilung beträgt die errechnete Protonenabschirmungskonstante 28,30 ppm in guter Übereinstimmung mit den experimentellen Werten (30.20, 30.03 + 0.60 ppm). Die Ergebnisse für die magnetische Suszeptibilität des Wassermoleküls sind gleichfalls in vernünftiger Übereinstimmung mit dem Experiment.
    Notes: Abstract The variation-perturbation uncoupled Hartree-Fock procedure of Karplus and Kolker is employed for the calculation of the second-order properties of the water molecule. The SCF MO LCGO ground state wave function was chosen and the first-order perturbed orbitals were approximated in the multiplicative form. The convergence of the method as well as the violation of the gauge independence are studied. For the preferred gauge origin at the electronic centroid the calculated proton shielding constant is 28.30 ppm and compares favourably with the experimental data (30.20, 30.03 ±0.60 ppm). The results for the magnetic susceptibility of the water molecule are also in reasonable agreement with experimental values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00528156
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Polarized basis sets and the calculation of infrared intensities from nuclear electric shielding tensors (1985)
    Springer
    Theoretical chemistry accounts 68 (1985), S. 431-444 
    Details
    ISSN: 1432-2234
    Keywords: Basis sets ; Perturbation-dependent basis sets ; Polarized basis sets ; Hellmann-Feynman theorem ; Infrared intensities ; Molecular properties ; H2O
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The idea of the basis set polarization which follows from the known dependence of basis set functions on the perturbation strength is applied to the calculation of the dipole moment derivatives with respect to nuclear displacements. The differentiation of the dipole moment function is replaced by the straightforward evaluation of derivatives of the intramolecular electric field with respect to the external electric field strength. The method and its efficiency are illustrated by a series of calculations of the dipole moment derivatives for the water molecule. Already a polarized basis set of 26 CGTO's derived from the minimal CGTO basis set provides fairly reasonable results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527668
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Approximate variation-perturbation calculations of the second-order molecular properties (1971)
    Springer
    Theoretical chemistry accounts 21 (1971), S. 159-167 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Das Variations-Störungsverfahren wird im Rahmen der CNDO/2-Näherung zur Berechnung von elektrischen Polarisierungstensoren zweiatomiger Moleküle herangezogen. Die Resultate ähneln denen des analogen, aber auf ab initio-Rechnungen basierenden Verfahrens mit einem minimalen Satz von Slaterfunktionen. Es ergibt sich, daß die Berechnung der Anisotropien nicht möglich ist, wohl aber die der räumlichen Mittelwerte.
    Notes: Abstract The variation-perturbation technique is applied to the calculation of the electric polarizability tensor of diatomic molecules within the CNDO/2 approximation. The results obtained in this paper are similar to those found in the non-empirical variation-perturbation approach within the minimal STO basis set. They are also compared with other CNDO/2 calculations and with existing experimental data. It follows from this comparison that the CNDO/2 variation-perturbation method does not allow for the calculation of the polarizability anisotropies. On the other hand, the rotational average of the polarizability tensor can be predicted in agreement with both the experimental data and nonempirical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00530213
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Proton magnetic shielding in H2O and (H2O)2 (1973)
    Springer
    Theoretical chemistry accounts 30 (1973), S. 257-265 
    Details
    ISSN: 1432-2234
    Keywords: Proton magnetic shielding ; Hydrogen bond NMR shift of water molecule and dimer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The proton magnetic shielding constants in the water molecule and its linear perpendicular dimer are computed from SCF-MO-LCGO wave functions by using the uncoupled Hartree-Fock variation-perturbation procedure due to Karplus and Kolker. The convergence of the calculated shielding constants as well as their gauge dependence is studied. The final results for 17-term polynomial variation function indicate that the best choice for the gauge origin corresponds to the molecular electronic centroid. The calculated proton magnetic shielding constant in the water molecule is in remarkable agreement with experimental data and favourably compares with the best coupled Hartree-Fock results. It follows from the calculations for the water dimer that the H-bond NMR-shift amounts in this case —1.0 ppm and qualitatively agrees with the experimental data for the liquid water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527616
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Electric properties of the chloride ion (1988)
    Springer
    Theoretical chemistry accounts 74 (1988), S. 185-194 
    Details
    ISSN: 1432-2234
    Keywords: Multipole polarizabilities ; Properties of Cl− ; Polarized basis sets ; MBPT calculations of properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dipole (α), quadrupole (C), and dipole-quadrupole (B) polarizabilities and the dipole hyperpolarizability (γ) of the chloride ion have been calculated by using the many-body perturbation theory approach and a series of large polarized GTO/CGTO basis sets. The complete fourth-order treatment of the electron correlation effects with a basis set comprising the s, p, d, f, and g functions gives: α=38.01 a.u., C=211.5 a.u., B=−5.14×103 a.u., and γ=128. 5×103 a.u. as compared to the corresponding SCF values (α=31.49 a.u., C=158.9 a.u., B=−2.92×103 a.u., γ=57.7×103 a.u.). The quenching of polarizabilities of the Cl− ion in solutions and ionic crystals is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527142
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Time-dependence of wave functions and the calculation of transition intensities (1989)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 35 (1989), S. 409-423 
    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 standard formalism of the perturbation theory for time-dependent perturbations follows from the assumption that the exact solution of the unperturbed time-independent problem is known. The consequences of this assumption are analyzed.Particular attention is given to the methods used for the evaluation of transition intensities. It is shown that the traditional intensity formula in most cases violates the assumptions underlying its derivation. It is shown that for the given ansatz concerning the form of the approximate wave function, the transition intensities should be determined from the variation treatment of the corresponding time-dependent problem. The wave functions of both states involved in the transition should be given the same amount of variation flexibility. This condition is satisfied if the transition intensity expression follows from the complete timedependent perturbation treatment of the perturbed system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560350306
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    CNDO calculations of diamagnetic shielding in molecules (1970)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 2 (1970), S. 63-69 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An approximate procedure for the calculation of diamagnetic shielding in molecules is presented. The method proposed is based on the ‘complete neglect of differential overlap’ (CNDO) molecular wave functions and is formulated according to the zero differential overlap (ZDO) approximation. The results obtained with several CNDO-type wave functions for diatomic and polyatomic molecules are in very good agreement with non-empirical SCF calculations. The 14N diamagnetic shielding constants in several molecules were computed and some approximations usually adopted in the interpretation of 14N chemical shifts are critically discussed. It was shown that in some cases the observed 14N chemical shifts cannot be interpreted solely in terms of the paramagnetic contribution to the shielding constant.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270020108
    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...