TU Darmstadt / ULB / TUbiblio

Molecular dynamics in perfluoro-n-eicosane. II. Components of disorder

Albrecht, T. ; Elben, H. ; Jäger, R. ; Kimmig, M. ; Steiner, R. ; Strobl, G. ; Stühn, B. ; Schwickert, H. ; Ritter, C. :
Molecular dynamics in perfluoro-n-eicosane. II. Components of disorder.
In: Journal of Chemical Physics, 95 (4) pp. 2807-2816.
[Artikel], (1991)

Kurzbeschreibung (Abstract)

The defect structure in the rhombohedral modification R of perfluoro-n-eicosane has been analyzed in a temperature-dependent x-ray and neutron scattering study. The analysis was based on an evaluation of Bragg-reflection intensities and of the diffuse scattering. Different components of disorder were detected and characterized. At the transition from the low temperature phase to modification R, rotation of the molecules about their long axes sets in. As shown by the azimuthal distribution of the diffuse scattering, rotations occur cooperatively with correlations between neighbors. The Debye-Waller factors measured for the layer reflections are indicative for a moderate roughening of the interfaces due to a restricted longitudinal diffusive motion. Molecules are perturbed by the formation of helix reversal defects. Evaluation of the diffuse scattering yields the associated finite azimuthal correlation length. There is also evidence for a continuous slow untwisting of the helix. With increasing temperature, it approaches the all-trans form.

Typ des Eintrags: Artikel
Erschienen: 1991
Autor(en): Albrecht, T. ; Elben, H. ; Jäger, R. ; Kimmig, M. ; Steiner, R. ; Strobl, G. ; Stühn, B. ; Schwickert, H. ; Ritter, C.
Titel: Molecular dynamics in perfluoro-n-eicosane. II. Components of disorder
Sprache: Englisch
Kurzbeschreibung (Abstract):

The defect structure in the rhombohedral modification R of perfluoro-n-eicosane has been analyzed in a temperature-dependent x-ray and neutron scattering study. The analysis was based on an evaluation of Bragg-reflection intensities and of the diffuse scattering. Different components of disorder were detected and characterized. At the transition from the low temperature phase to modification R, rotation of the molecules about their long axes sets in. As shown by the azimuthal distribution of the diffuse scattering, rotations occur cooperatively with correlations between neighbors. The Debye-Waller factors measured for the layer reflections are indicative for a moderate roughening of the interfaces due to a restricted longitudinal diffusive motion. Molecules are perturbed by the formation of helix reversal defects. Evaluation of the diffuse scattering yields the associated finite azimuthal correlation length. There is also evidence for a continuous slow untwisting of the helix. With increasing temperature, it approaches the all-trans form.

Titel der Zeitschrift, Zeitung oder Schriftenreihe: Journal of Chemical Physics
Band: 95
(Heft-)Nummer: 4
Fachbereich(e)/-gebiet(e): Fachbereich Physik
Fachbereich Physik > Festkörperphysik, Condensed matter physics
Hinterlegungsdatum: 26 Feb 2010 13:35
Export:

Optionen (nur für Redakteure)

Eintrag anzeigen Eintrag anzeigen