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  • 1
    Digitale Medien
    Digitale Medien
    Temperature and field dependence of the charge injection from metal electrodes into random organic media (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 3941-3944 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We consider the average injection rate from a metal electrode into disordered organic media, and its field dependence for a fixed density of carriers in the metal. At sufficiently high field the injection occurs through particular pathways, lowering the energetic barrier between the metal Fermi energy and the molecular levels of the organic layer. Assuming a Gaussian distribution of random energies, we find the dependence of current j on field E j∝exp(βE) in the relevant domain of electric fields. This behavior agrees both with numerical simulations of three-dimensional systems and with experimental data. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1290697
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  • 2
    Digitale Medien
    Digitale Medien
    Jastrow corrected time-dependent self-consistent field approximation (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7610-7621 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: An improved approximation to the time-dependent Schrödinger equation is developed by correcting the time-dependent self-consistent field ansatz with a Jastrow prefactor defined via a set of variationally determined time-dependent parameters and a linearly independent set of prespecified spatial functions. The method is applicable in any number of dimensions, conserves norm and energy, is without parametric singularities, possesses an internal estimate of the accuracy, and has computational costs that scale algebraically with the number of degrees of freedom. The new formalism is applied to a two-dimensional double well potential to demonstrate the improved accuracy of the method. An extension of the method to electronically nonadiabatic problems is also presented. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.478673
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  • 3
    Digitale Medien
    Digitale Medien
    The relativistic Dirac–Coulomb–Fock effect on atomization energies (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7123-7126 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We have used a second-order perturbation treatment of the Dirac–Coulomb–Hartree–Fock method to estimate relativistic contributions to energies in the G2/97 test set. The one-electron relativistic effect on atomization energies of molecules containing first- and second-row atoms nearly always reduces binding. When the relativistic corrections are included in G3 theory and assessed on the G2/97 test set, there is little change in overall performance. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.478615
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  • 4
    Digitale Medien
    Digitale Medien
    Glass formation and local disorder: Amorphization in planar clusters (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 7901-7906 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Structural aspects of amorphization in a cluster model of a disordered phase are presented. Molecular dynamics simulations were done within a "mobile cluster static boundary" model, in which static, disordered particles at the boundary of the simulation cell cause particles within the cell to adjust themselves structurally. With sufficient boundary disorder, both the radial distribution function and the orientational order parameter show onset of amorphization behavior. For Lennard-Jones particles, which are not good glass formers, the amorphization occurs only within a certain healing distance of the disordered boundary. With increasing boundary disorder, the orientational correlation function and the radial distribution function indeed show orientational phase scrambling, disappearance of long-range order, and the onset of glass-like amorphized structure. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.477437
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  • 5
    Digitale Medien
    Digitale Medien
    Spin effects on the luminescence yield of organic light emitting diodes (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6092-6102 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The influence of the excitation spectrum on the quantum yield is investigated for organic molecules used in light emitting diodes (LEDs). The significance of the competition between radiative and nonradiative recombination channels is pointed out. A system of master equations is proposed to describe the relaxation of lower levels of the excited molecule, and the solution for the fluorescence yield is obtained assuming relatively weak vibronic coupling. The results are used to interpret the experimental data in oligothiophenes, and general approaches are proposed to increase the relative weight of the radiative decay channel and correspondingly enhance the working properties of organic light emitting diodes. In particular, the fluorescence quantum yield can exceed the simple estimate of 0.25. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.477236
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  • 6
    Digitale Medien
    Digitale Medien
    Electron Transfer in Mixed-Valence Clusters: Spin-Dependent Dielectric Loss and Hamiltonian Parameters (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 2656-2661 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100009a024
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  • 7
    Digitale Medien
    Digitale Medien
    Atomic classes: Rearrangement processes (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 6519-6529 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Glass formation and glassy dynamics are studied using a mobile cluster, static boundary model. For the two-dimensional Lennard-Jones glass, we examine the nature of the rearrangement processes that characterizes glassy dynamics, the correlation functions of the hexadic order parameter, the temperature dependence of the distribution of relaxation times, and the dependence of these properties both on the disorder within the static boundary and on the temperature. The mobile cluster passes from a low temperature disordered material to an intermediate temperature amorphized material to a high temperature liquid; during this thermal history, the distribution of relaxation times exhibits nonexponential behavior in the glassy region, and becomes Debye-like in the liquid phase. We see a chain of local structural rearrangements in a small cluster of eight particles representing characteristic elementary kinetic events in this very simple model of glass behavior. The possibility to interpret these events in terms of defect motion is discussed. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.478555
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  • 8
    Digitale Medien
    Digitale Medien
    Electron correlation in chemical bonds (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 4014-4019 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We study the correlation energy in the H2 molecule as a function of bond distance and the electron coupling parameter that modifies the strength of electron–electron repulsion. For the unscaled electron repulsion we find an unusual complexity of the correlation energy dependence on the bond distance. This complexity remains if the electron repulsion is scaled down. We pay particular attention to the range of bond distances near the H2 equilibrium geometry. We confirm that good performance of the modern exchange–correlation functionals in molecular geometry optimization is due to the cancellation of errors between the exchange and correlation components. These components have different functional dependence on the electron coupling parameter, so the cancellation of errors no longer occurs when the electron repulsion is scaled down. This observation is important if the adiabatic connection theorem is used to construct the exchange–correlation functionals. It is also relevant for the performance of exchange–correlation functionals to study ionic interactions. The performance of the correlation operator in the molecular environment is also investigated and discussed. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.480950
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  • 9
    Digitale Medien
    Digitale Medien
    6-31G* basis set for atoms K through Zn (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 1223-1229 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Medium basis sets based upon contractions of Gaussian primitives are developed for the third-row elements K through Zn. The basis functions generalize the 6-31G and 6-31G* sets commonly used for atoms up to Ar. They use six primitive Gaussians for 1s, 2s, 2p, 3s, and 3p orbitals, and a split-valence pair of three and one primitives for valence orbitals, which are 4s and 5p for atoms K and Ca, and 4s, 4p, and 3d for atoms Sc through Zn. A 6-31G* set is formed by adding a single set of Gaussian polarization functions to the 6-31G set. They are Cartesian d-functions for atoms K and Ca, and Cartesian f-functions for atoms Sc through Zn. Comparison with experimental data shows relatively good agreement with bond lengths and angles for representative vapor-phase metal complexes. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.476673
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  • 10
    Digitale Medien
    Digitale Medien
    Monte Carlo methods for short polypeptides (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9177-9191 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Nonphysical sampling Monte Carlo techniques that enable average structural properties of short in vacuo polypeptide chains to be calculated accurately are discussed. Updating algorithms developed for Monte Carlo studies of flexible polymer chains are modified and adapted for polypeptide chain systems to improve conformational sampling. Utilizing these methods, the effect of bond angle and bond length constraints in Monte Carlo simulations are examined and it is demonstrated that angle constraints bias structural averages without greatly reducing the computational work. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.477471
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