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  • 1
    Electronic Resource
    Electronic Resource
    Dynamics of polymer solutions and melts. Reptation predictions and scaling of relaxation times (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 7726-7740 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The bond fluctuation model on the simple cubic lattice is studied by Monte Carlo simulations on a multitransputer array, for polymer volume fractions φ in the range 0.025≤φ≤0.500 and chain lengths N in the range 20≤N≤200. Extensive data are presented on the dynamics of monomer displacements, center-of-gravity displacements, and relaxation times. This study is complementary to previous work, in which the crossover scaling properties of the chain linear dimensions, structure factor, and self-diffusion constant were tested for the same athermal model. The simulation technique takes both excluded volume interactions and entanglement constraints into account, but ignores hydrodynamic forces. Our results describe the crossover from Rouse behavior of swollen chains (τ∼N1+2ν, ν being the exponent describing the radius R of the chains, R∼Nν ) to reptation, τ∼N3. Since the excluded volume screening length is found to be smaller than the tube diameter by a factor of about 3, the rescaled times Wτ/N1+2ν decrease first as a function of the scaled chain length N˜∼Nφ1/(3ν−1), before they increase due to the onset of reptation. Additional evidence for reptative behavior is found by identifying the several successive crossovers in the time-dependent displacements predicted by de Gennes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461346
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  • 2
    Electronic Resource
    Electronic Resource
    Structure-property correlation of polymers, a Monte Carlo approach (1991)
    s.l. : American Chemical Society
    Macromolecules 24 (1991), S. 6332-6334 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00023a041
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  • 3
    Electronic Resource
    Electronic Resource
    Description of noble gas diffusion in a polymer matrix by a hopping model (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 9550-9557 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a new heuristic model which describes the diffusion of noble gas atoms inside a polymer matrix. The motion of the gas atoms consists of movements inside small areas called traps and of hops between different traps. Whether an atom enters another trap during a molecular dynamics (MD) simulation is determined by observing a new quantity called cage overlap. This criterion is independent of size, time, and temperature scales of the system. The resulting motions are quantitatively described by probability distributions and correlation functions. We measure these distributions for three example systems of helium, argon, and krypton atoms inside a polyethylene matrix using MD simulations. Then we verify the model by comparing results from direct simulations of the hopping model with initial results from the MD. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476403
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  • 4
    Electronic Resource
    Electronic Resource
    Surface tension of amorphous polymer films (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 10075-10081 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study the surface tension for thin, amorphous polymer films by means of computer simulation. Using molecular dynamics, we present surface tension measurements via the fluctuation spectrum of capillary waves in the long-wavelength limit for sufficiently large systems. We find good agreement with a theory based on continuum mechanics. In addition, we observe the spreading of the surface thickness with increasing lateral system size, an effect which allows another estimate of the surface tension. Furthermore, we studied the correlation between two surfaces and measured the transverse length scale by varying the film thickness. We also present data of the temperature dependence of the bulk density of the polymer film and the thickness of the surface region in the regime above the glass transition temperature. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477683
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  • 5
    Electronic Resource
    Electronic Resource
    Finite-size scaling in a microcanonical ensemble (1988)
    Springer
    Journal of statistical physics 53 (1988), S. 795-823 
    Details
    ISSN: 1572-9613
    Keywords: Microcanonical ensemble ; finite-size scaling ; two-dimensional Ising model ; transputers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The finite-size scaling technique is extended to a microcanonical ensemble. As an application, equilibrium magnetic properties of anL×L square lattice Ising model are computed using the microcanonical ensemble simulation technique of Creutz, and the results are analyzed using the microcanonical ensemble finite-size scaling. The computations were done on the multitransputer system of the Condensed Matter Theory Group at the University of Mainz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01014226
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamic percolation transition induced by phase separation: A Monte Carlo analysis (1987)
    Springer
    Journal of statistical physics 49 (1987), S. 1053-1081 
    Details
    ISSN: 1572-9613
    Keywords: Percolation ; phase separation ; Monte Carlo simulation ; lattice gas model ; finite-size scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The percolation transition of geometric clusters in the three-dimensional, simple cubic, nearest neighbor Ising lattice gas model is investigated in the temperature and concentration region inside the coexistence curve. We consider “quenching experiments,” where the system starts from an initially completely random configuration (corresponding to equilibrium at infinite temperature), letting the system evolve at the considered temperature according to the Kawasaki “spinexchange” dynamics. Analyzing the distributionn l(t) of clusters of sizel at timet, we find that after a time of the order of about 100 Monte Carlo steps per site a percolation transition occurs at a concentration distinctly lower than the percolation concentration of the initial random state. This dynamic percolation transition is analyzed with finite-size scaling methods. While at zero temperature, where the system settles down at a frozen-in cluster distribution and further phase separation stops, the critical exponents associated with this percolation transition are consistent with the universality class of random percolation, the critical behavior of the transient time-dependent percolation occurring at nonzero temperature possibly belongs to a different, new universality class.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01017560
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  • 7
    Electronic Resource
    Electronic Resource
    Monte Carlo study of the ising model phase transition in terms of the percolation transition of “physical clusters” (1990)
    Springer
    Journal of statistical physics 60 (1990), S. 585-618 
    Details
    ISSN: 1572-9613
    Keywords: Percolation ; “physical clusters” ; Ising model ; Monte Carlo simulation ; finite-size scaling ; Fortuin-Kasteleyn representation ; Swendsen-Wang algorithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Finite squareL×L Ising lattices with ferromagnetic nearest neighbor interaction are simulated using the Swendsen-Wang cluster algorithm. Both thermal properties (internal energyU, specific heatC, magnetization 〈|M|〉, susceptibilityχ) and percolation cluster properties relating to the “physical clusters,” namely the Fortuin-Kasteleyn clusters (percolation probability 〈P ∞〉, percolation susceptibilityχ p, cluster size distributionn l) are evaluated, paying particular attention to finite-size effects. It is shown that thermal properties can be expressed entirely in terms of cluster properties, 〈P ∞〉 being identical to 〈|M|〉 in the thermodynamic limit, while finite-size corrections differ. In contrast,χ p differs fromχ even in the thermodynamic limit, since a fluctuation in the size of the percolating net contributes toχ, but not toχ p. NearT c the cluster size distribution has the scaling properties as hypothesized by earlier phenomenological theories. We also present a generalization of the Swendsen-Wang algorithm allowing one to cross over continuously to the Glauber dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025984
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  • 8
    Electronic Resource
    Electronic Resource
    Buchbesprechungen (1985)
    Springer
    Zeitschrift für angewandte Mathematik und Physik 36 (1985), S. 635-636 
    Details
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00945305
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  • 9
    Electronic Resource
    Electronic Resource
    A new model with non-spherical interactions for dense polymer systems (1995)
    Springer
    Journal of computer-aided materials design 2 (1995), S. 1-8 
    Details
    ISSN: 1573-4900
    Keywords: Monte Carlo ; Modelling ; BPA-PC ; Ellipsoidal model ; Non-spherical interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary We introduce a new general model for the simulation of dense macromolecular systems. It consists of basic ellipsoidally shaped units stringed together to form chains, including branched and side chains. The ellipsoidally shaped unit can vary in its principal axes, allowing for flexible modeling of a chain. The variation in the main principal axis is used for the intramolecular potential of the bond type. Intramolecular units interact through a harmonic bond-angle potential and the intermolecular interaction is modelled by a confocally decreasing Lennard-Jones potential. We present the model for the special case of a polycarbonate and indicate the generalization to other cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00701677
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  • 10
    Electronic Resource
    Electronic Resource
    Scaling and mean-field-like behaviour in phase separation processes (1985)
    Springer
    The European physical journal 61 (1985), S. 311-323 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Extensive Monte Carlo calculations are used to study the still not well understood process of phase separation in binary systems. The results show that for a separation dominated by long-wavelength fluctuations a mean-field description holds in certain concentration regions. This, however, is only true for short times after the system has been brought into a non-equilibrium state. A crucial parameter is the interaction range. It determines the region and the time where the mean field description is valid. At later times the structure factor exhibits dynamical scaling. Scaling is also investigated for the metastable states. The results are applicable to polymer blends with long chains or binary alloys with long-range forces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01317798
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