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  • 1
    Electronic Resource
    Electronic Resource
    Triplet interactions in star polymer solutions (2000)
    Springer
    The European physical journal 2 (2000), S. 311-318 
    Details
    ISSN: 1292-895X
    Keywords: PACS. 82.70.Dd Colloids – 64.60.Fr Equilibrium properties near critical points, critical exponents – 61.20.Ja Computer simulation of liquid structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We analyze the effective triplet interactions between the centers of star polymers in a good solvent. Using an analytical short-distance expansion inspired by scaling theory, we deduce that the triplet part of the three-star force is attractive but only 11% of the pairwise part even for a close approach of three star polymers. We have also performed extensive computer simulations for different arm numbers f to extract the effective triplet force. The simulation data show good correspondence with the theoretical predictions. Our results justify the effective pair potential picture even beyond the star polymer overlap concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101890050013
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  • 2
    Electronic Resource
    Electronic Resource
    An exactly soluble model for interfacial kinetics (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 674-678 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study an exactly soluble model for planar interfacial kinetics for both locally conserved and nonconserved order parameters, where the Landau–Ginzburg potential is approximated by two parabolas. Long-range interactions with arbitrary interaction kernels are included. In particular, the relaxation of the initial order parameter interfacial profile to its equilibrium profile is considered. Furthermore, the steady-state solution of planar interfacial growth for a nonconserved order parameter is determined. Here, the influence of a second nonconserved order parameter is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459515
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  • 3
    Electronic Resource
    Electronic Resource
    The vibron–phonon sidebands in the Fourier-transform infrared spectra of the molecular crystal CO2 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5309-5314 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: FTIR investigations on polycrystalline CO2 at various temperatures show Stokes and anti-Stokes sidebands coupled to the vibrational modes v3, v2, and v+/v− (Fermi dyad). The latter is infrared forbidden and may be eliminated from spectra of good quality polycrystalline films. The main peaks in the structure of the sidebands may be assigned to phonons from points of highest symmetry in the Brillouin zone. The vibron–phonon coupling process is mode specific and driven by electrical anharmonicity in case of v+ and v−. For the infrared allowed fundamentals, and especially at the Γ point, the coupling process is also driven by mechanical anharmonicity. The dispersion of these internal modes at k=0 influences the coupled phonons and thus the one phonon density of states is correctly mirrored by the v+ and v− sidebands only.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456435
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  • 4
    Electronic Resource
    Electronic Resource
    Vibron–phonon excitations in the molecular crystals N2, O2, and CO by Fourier transform infrared and Raman studies (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8565-8575 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The influence of temperature on the vibron–phonon combination band in the Raman and infrared (ir) spectra of the N2 and O2 molecular crystals supports the possibility of an assignment of the main features in the sideband to strong contributions from translational and librational phonons in points of high symmetry in the reciprocal lattices. The temperature behavior in Raman and ir sideband spectra in α-N2 is attributed to distinct anharmonicities in the isotropic and anisotropic parts of the potential and to different coupling mechanisms, resulting in a librational and translational weighted one-phonon density of states (DOS). In contrast, such an interpretation is not feasible for the poorly structured CO sideband, although the crystal structures of CO and N2 are nearly identical. The difference is attributed to strong anharmonicities and the presence of a weak dipole moment in the former, which introduces strong lattice mode coupling. Crossing the α–β phase transition has marked effects on the sidebands (shape, intensity) in both N2 and O2 crystals, which reflects the orientational disorder in the β phase of the former and the importance of the change in magnetic interactions in the latter. For both molecular crystals, the vibron–phonon coupling to the electromagnetic field is stronger in the ir than in the Raman spectra and seems predominantly due to electrical anharmonicities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459294
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  • 5
    Electronic Resource
    Electronic Resource
    Sideband modeling in molecular crystals N2 and CO2 (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 5703-5711 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibron-phonon excitation bands, phonon sidebands to the zero phonon line, mirror the one-phonon density of states g(ω) calculated in the harmonic approximation. The origin of bands in the sideband is investigated, e.g., phonon contributions from librational and translational modes or phonons at special points of the Brillouin zone. The temperature-dependent structure of the sideband (frequency shifts, line broadening) is due to anharmonic processes which modify g(ω): Temperature-dependent frequency shifts of maxima in the sideband are shown to depend mainly on the volume effect, whereas line broadening is due to phonon–phonon interactions, which are simulated in the lattice dynamics calculations of g(ω) by a special modeling procedure. Compared to the CO2 solid, effects are more pronounced in the N2 crystal due to the presence of strong mechanical and electrical anharmonicities. The latter give rise to multiphonon contributions in the vibron-phonon excitation process. Intensity changes with temperature can be explained by the thermal weighting of the one-phonon density of states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462669
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  • 6
    Electronic Resource
    Electronic Resource
    Spectral properties of an optical polaron in a magnetic field (1988)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 29 (1988), S. 1498-1504 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: An optical polaron, which is exposed to a homogeneous magnetic field, is considered. Making use of functional analytical methods of Fröhlich [Fortschr. Phys. 22, 159 (1974)], it is proved that the ground-state energy, the magnetic polaron mass, and the number of virtual phonons in the ground state are analytical functions of the electron–phonon coupling parameter and the magnetic field strength. Consequently, a discontinuous stripping transition, which was claimed recently by several authors, does not exist. In fact, some authors have stated that the discontinuities they encounter might indeed be artifacts due to the approximation. The spectrum of the momentum-decomposed Fröhlich Hamiltonian is analyzed; bounds and smoothness properties of the ground state and the discrete excited states are derived. All results hold also for lower spatial dimensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.527893
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  • 7
    Electronic Resource
    Electronic Resource
    Analytical behavior of the ground-state energy and pinning transitions for a bound polaron (1988)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 29 (1988), S. 1505-1513 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Spectral properties of a three-dimensional optical polaron, bound in an external potential, are studied. If the associated one-particle Hamiltonian has a bound state, it is proved that the ground-state energy of the polaron and expectation values of the ground state are analytical functions of the coupling parameter α and the potential strength β. Especially in the case of a Coulomb potential, all changes in the polaron state are continuous, disproving claims of several variational calculations. If, on the other hand, the one-particle Hamiltonian has no bound state, the existence of a pinning transition is shown for the polaron. As physically relevant potentials for the pinning transition, a spherical square well and a screened Coulomb potential are considered. Their phase diagrams are given in the effective-mass approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.527894
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  • 8
    Electronic Resource
    Electronic Resource
    A note on the existence of phase transitions in finite-site Peierls-Hubbard systems (1988)
    Springer
    The European physical journal 71 (1988), S. 219-224 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss spectral properties of a generalizedN-siten-electron Peierls-Hubbard system and examine the possibility of phase transitions of the ground state. ForN=2, it is proved that no phase transition exists. ForN〉2, the only possibility of a phase transition is a crossing of two discrete energy levels corresponding to different symmetries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01312792
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of gravity on surface melting (1990)
    Springer
    The European physical journal 79 (1990), S. 441-444 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The influence of gravity on planar surface melting is studied if the surface normal is parallel to the gravitational acceleration. We find that gravity prevents complete melting. At the triple point, the solid is covered with a liquid film whose thickness is of the order of a micrometer. We suggest to use a centrifuge with high centripetal acceleration in order to observe the deviation from the usual melting law experimentally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437655
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  • 10
    Electronic Resource
    Electronic Resource
    Multiple order parameter theory of surface melting: A van der Waals approach (1990)
    Springer
    The European physical journal 79 (1990), S. 109-118 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We describe a van der Waals approach with multiple order parameter for surface melting near the triple pointT T which is based on density functional theory for bulk freezing. The occurrence of surface-induced melting, non-melting or blocked (incomplete) melting is governed by the specific form of the long-ranged tail in the interparticle potential. In the case of melting, the residual crystallinity at the vapor side of the quasi-liquid layer is shown to decay with a stretched exponential (power) law inT T -T for long-(short-) ranged interparticle forces
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01387832
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