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  • 1
    Electronic Resource
    Electronic Resource
    Cartesian correlation times for NMR AX2 spin systems (1985)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 107 (1985), S. 6695-6698 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00309a045
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  • 2
    Electronic Resource
    Electronic Resource
    Rotational dynamics of flexible alkanes. An NMR coupled relaxation and a Brownian dynamics study (1985)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 107 (1985), S. 6698-6707 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00309a046
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  • 3
    Electronic Resource
    Electronic Resource
    The Onsager theory of the isotropic–nematic liquid–crystal transition: Biaxial particles in uniaxial phases (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 4546-4556 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Dense fluids of biaxial hard convex bodies exhibit a phase transition from an isotropic to a nematic (I–N) liquid–crystalline state. In the Onsager theory, the I–N transition is attributed to the tendency of pairs of molecules to minimize their excluded volume (or second virial coefficient, B2 ). In the present work, the mutual orientation dependence of B2 is calculated for hard biaxial ellipsoids and is expressed in a Wigner function expansion. Orientational distribution functions are determined for the Onsager model and for the Lee model, which incorporates some density correlations beyond those in the Onsager theory. In the uniaxial phase of biaxial molecules, the two nonzero order parameters calculated on the basis of hard-body models are in approximate accord with the findings of Maier–Saupe based theories. Introduction of biaxiality into a body has a pronounced effect: both the 〈P2〉 order parameter and the first orderness of the I–N transition are greatly reduced from that of comparable uniaxial bodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460609
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  • 4
    Electronic Resource
    Electronic Resource
    The Onsager theory of the isotropic–nematic liquid crystal transition: Incorporation of the higher virial coefficients (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4254-4265 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the Onsager theory for the phase transition from the isotropic fluid to the nematic liquid crystal phase, the Helmholtz free energy of a fluid of hard convex bodies (HCBs) is expressed as the sum of an entropy of a mixing-like term and an energy-like term (from the interaction of the HCBs). Whereas the Onsager theory expresses the interaction term in a virial expansion and determines the consequences of B2 alone, here we extend that treatment to incorporate B3 (with its attendant dependence on the mutual orientation of three HCBs). For HCBs (and specifically for D∞h ellipsoids) with large aspect ratios (5:1 or greater), the incorporation of B2 and B3 suffices to predict the variation of the order parameter 〈P2[cos(θ)]〉 with density in accord with the Monte Carlo (MC) results of Allen and Wilson. As the aspect ratio decreases (from 5:1) to more spherical molecules (say 3:1), virial coefficients of higher order than B3 contribute to the interaction term and their effect is represented in part by the y-expansion (or resummation) theory proposed by Barboy and Gelbart. In this y-expansion–third virial-Onsager theory, the predicted transition densities are in accord with the MC values of Frenkel and Mulder for prolate ellipsoids. Neither the y expansion nor the direct B2 and B3 theories find the phase diagram (i.e., transition density and order parameter regarded as a function of aspect ratio) to be symmetric for prolate and oblate ellipsoids. The dependence of B3 on the mutual orientation of the ellipsoids is also discussed and previous work is also addressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458758
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  • 5
    Electronic Resource
    Electronic Resource
    Pair dynamics in hard sphere fluids: Recollisional time correlation functions (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1275-1284 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics calculations are reported on dense hard sphere fluids at three packing fractions (η=0.30,0.40,0.48). Attention is directed to the analysis of correlated recollisions of pairs of particles. The short time dynamics [t(approximately-equal-to)0(τc) where τc=1/collision frequency] is governed by correlated backscattering collisions as evidenced by persistence of vector time correlations. For longer times a crossover takes place from the correlated backscattering regime (or geminate recombination) to the diffusive-like regime (nongeminate recombination) in which vector correlations decay faster than scalar correlations. Recollisional events are categorized as first recollisions, second recollisions, and all recollisions. The resulting correlation functions exhibit different evolutionary time scales. Contributions to the time correlation functions (tcfs) from collision sequences involving three and four particles are also separated and analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458137
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamics of nonspherical bodies: Relative diffusion of a sphere with respect to a fixed convex body (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4912-4919 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A Smoluchowski equation is derived that depicts the relative diffusion of a sphere with respect to a fixed nonspherical convex body. The transport equation is expressed in terms of the surface-to-surface separation s, measured along the surface normal k. In this coordinate system, the effects of particle shape anisotropy can be subsumed by an appropriate mapping of the radius of the convex excluded volume surface onto that of an equivalent spherical system. Steric effects in diffusion-controlled reaction rates and shape anisotropy corrections to the recollision kinetic theory of rotation are analyzed in light of the chosen coordinates and the explicit Smoluchowski equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456731
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamics of pair diffusion in hard sphere fluids (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1804-1811 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Kinetic theory is applied to the analysis of the position and frequency dependence of the friction coefficient describing pair diffusion of hard spheres in their parent fluid. The high frequency friction is found to increase monotonically with internuclear separation from its contact value (at R=σ) up to a maximum at R=2σ, whereupon the friction attains its Enskog value. For low frequencies, the pair friction is a sum of the background high frequency part and caging and hydrodynamic contributions. Both caging and hydrodynamic effects exhibit different R dependences, the former an increasing function of separation (up to R=2σ) and the latter a decreasing function (as σ/R for R〉σ).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456022
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  • 8
    Electronic Resource
    Electronic Resource
    Translational dynamics in simple dense fluids. II. Self-diffusion (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1812-1818 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Our previous kinetic theory of dense fluids is applied to the calculation of the self-diffusion coefficient of a hard sphere in a hard sphere bath. Corrections beyond an Enskog theory are obtained by the expansion of the recollision operator in terms of a truncated set of four functions; the properties and utility of these four functions, two representing caging and the other two, momentum flows, are determined by the comparison of the computed friction coefficients with the molecular dynamics of Alder et al. Agreement of the present work with existing theories is good, whereas agreement with the molecular dynamics results is still only qualitative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456023
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  • 9
    Electronic Resource
    Electronic Resource
    A kinetic theory of collision-induced depolarized light scattering (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 685-691 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The collision-induced depolarized light scattering spectrum arising from the dipole–induced dipole (DID) interactions in atomic fluids has been calculated using kinetic theory methods. The theory contains no adjustable parameters and requires only the temperature, density, and collision diameter as input. Above 25 cm−1, the calculated line shape was found to be in excellent agreement with the spectrum obtained from a hard-sphere molecular dynamics simulation, with the same model for the interaction-induced polarizability. The domain of applicability of the approximations used in reducing the theory to a tractable form was carefully evaluated. The methods developed should be applicable to other intermolecular correlation functions, such as those observed in vibrational relaxation and interaction-induced infrared spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455190
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  • 10
    Electronic Resource
    Electronic Resource
    Erratum: A simple kinetic theory model of reactive collisions. IV. Laboratory fixed orientational cross sections [J. Chem. Phys. 87, 3865 (1987)] (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3401-3401 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454766
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