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
    Quantum chemistry and molecular engineering of oligomeric and polymeric materials for optoelectronics (1991)
    s.l. : American Chemical Society
    Chemical reviews 91 (1991), S. 843-865 
    Details
    ISSN: 1520-6890
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/cr00005a011
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Study of excited states of polyethylene in the Hartree–Fock, Tamm–Dancoff, and random-phase approximations (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 6831-6836 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report calculations of the excitonic spectra of all-trans polyethylene in the Hartree–Fock, Tamm–Dancoff, and random-phase approximations. For the formulation of approximations beyond Hartree–Fock level, we have used the particle–hole propagator technique. In the first case the interaction between the excited electron and hole is neglected and in the latter two cases it is taken into account at first order in electron–electron interaction. Using the 3–21G atomic basis set, the elementary gap is reduced from about 17 eV at the Hartree–Fock level to 13 eV in the Tamm–Dancoff approximation. The spectra in both approximations are also different. The difference between the results obtained in the Tamm–Dancoff and the random-phase approximations is very small. We discuss the densities of exciton states for different exciton quasi momenta (K=0 or K=π/a), different band interactions and different spins. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469119
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Long-range effects in optimizing the geometry of stereoregular polymers. II. Hydrogen fluoride chains as a working example (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5324-5330 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We use linear hydrogen fluoride chains to evaluate the efficiency of the long-range approach developed in the first paper of this series. A wide panel of tests and comparisons are carried out in order to understand the influence of the parameters on the quality of the forces and the accuracy of the optimized geometry. The long-range corrections are demonstrated to be essential for tight optimizations as well as to fasten the calculation procedure. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479791
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Long-range effects in optimizing the geometry of stereoregular polymers. I. Formalism (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5306-5323 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop an original methodology to calculate analytically the long-range (LR) Coulombic effects to be included in Hartree–Fock forces computed on stereoregular polymers. The technique presented, based on multiple Taylor series expansions, is completely general and can be easily extended to all orders of expansion and to geometrical derivatives of higher order. In the McMurchie Davidson or similar schemes, the LR terms are added directly to Hermite integrals and LR effects are naturally considered during the computation of the energy and its derivatives. Each type of derivative (nuclear-repulsion energy, overlap and kinetic energy integrals, electron–nuclear attraction and two-electron integrals) is examined to quantify the impact of LR corrections. It turns out that the lattice sums of the gradients evaluated on a model macromolecule converge much faster when including those corrections. In addition, the dependence of the energy with respect to the unit cell length is for the first time considered in full details. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479790
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Structure and molecular modeling of GABAA receptor antagonists (1992)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 35 (1992), S. 1969-1977 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00089a005
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Vibrational polarizability of polyacetylene chains (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 10796-10807 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Within the double harmonic oscillator approximation, ab initio vibrational contributions to the static electric dipole polarizability have been computed for the all-trans polyacetylene chains homologous series. Atomic basis set and electron correlation effects have been studied on ethylene and trans-butadiene as well as the use of semiempirical Hamiltonians. By using the 6-31G* atomic basis set within the Hartree–Fock and the second order Møller–Plesset procedures as well as by using semiempirical Austin model 1 Hamiltonians, the evolution with chain length of the vibrational polarizability per structural unit has been investigated and compared to the electronic contribution. Although smaller than the electronic contributions (αvibration≈10% αelectronic), the longitudinal component to the polarizability presents a similar exaltation as chain length grows, but a slower saturation to an asymptotic value per unit cell. Inclusion of electron correlation via the second order Møller–Plesset technique turns out to reduce the longitudinal component calculated at the Hartree–Fock level, but to increase the transversal and perpendicular components. Whereas it reproduces correctly the evolution with chain length of the vibrational polarizability tensor components, the Austin model 1 technique underestimates the longitudinal term and overestimates the perpendicular term. The major contribution to the vibrational polarizability results from large charge fluxes associated with asymmetric stretching motions of the carbon backbone and with the torsion motions presenting very low vibrational frequencies. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467830
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Role of collective modes in vibrational polarizabilities and hyperpolarizabilities of polyacetylene and other quasilinear polymers (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 4125-4136 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It is shown that the low frequency collective modes of quasilinear polymers can contribute to the vibrational polarizability and hyperpolarizability despite the fact that their infrared or Raman intensity vanishes in the infinite chain limit. The most significant of these modes are characterized and the dynamic vibrational nonlinear optical (NLO) properties are obtained, at the doubly harmonic Hartree–Fock level of approximation, from static field calculations on polyacetylene as well as polyyne, polysilane, and polyethylene. Comparison is made to a pair of unit cell modes, one Raman-active and the other infrared-active, that are expected to generate a large vibrational hyperpolarizability. The combined effect of the collective and unit cell vibrations is potentially of considerable importance for the enhancement of NLO properties. Further studies are suggested to exploit this potential. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471540
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Vibrational and electronic second hyperpolarizabilities of all-trans polysilane chains (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 4624-4637 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational (γLv) and electronic (γLe) longitudinal second hyperpolarizabilities of increasingly large polysilane chains are determined at the Hartree–Fock 6-31G level by adopting both the double harmonic oscillator approximation and the infinite optical frequency finite field relaxation procedure. The relative importance of the electronic, Raman, infrared/hyperRaman and lowest-order anharmonicity contributions to the second hyperpolarizability is evaluated for the most common nonlinear optical (NLO) processes. At the double harmonic oscillator level of approximation the most contributing vibrational normal modes to γLv are characterized as a function of the polysilane chain length. Comparisons with experimental and other theoretical studies are carried out in what concerns the infrared and Raman vibrational spectra as well as the NLO properties of various oligosilanes and polysilanes. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477067
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Ab initio band structure of polymethineimine isomers (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1023-1030 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio crystal orbital calculations have been performed on stereoregular polymethineimine (PMI) at the restricted Hartree-Fock/6-31G level. Since the optimized geometries of the parent oligomers show only small energy differences, four isomers, namely, trans-transoïd (TT), cis-transoïd (CT), trans-cisoïd (TC) and helical (HEL) have been studied to point out the geometry-dependences of the band structure, density of states (DOS) and polarizability. Some of these could be helpful for identifying the isomers. It turns out that the DOS makes the TT and CT isomers distinguishable, whereas the TC and HEL isomers present very similar DOS. Moreover, it is shown that the longitudinal polarizability per unit cell increases in the order HEL, TC, CT and TT. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475497
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    From uncoupled to coupled Hartree–Fock polarizabilities of infinite polymeric chains. Pariser–Parr–Pople applications to the polyacetylene chains (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8330-8337 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A general method is formulated to compute the asymptotic longitudinal polarizabilities of infinite systems. This procedure is an extension to infinite systems of the molecular random-phase-approximation method which provides coupled Hartree–Fock values and thus takes into account the field-induced electron reorganizational effects. It is shown that the Genkin–Mednis uncoupled method corresponds to the drastic approximation of the coupled one where there is no electron reorganization. By looking at the asymptotic polarizabilities as the convergence values of the oligomeric results, the method is tested for polyacetylene chains in the Pariser–Parr–Pople approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462337
    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...