Albrecht, T. and Elben, H. and Jäger, R. and Kimmig, M. and Steiner, R. and Strobl, G. and Stühn, B. and Schwickert, H. and Ritter, C. (1991):
Molecular dynamics in perfluoro-n-eicosane. II. Components of disorder.
95, In: Journal of Chemical Physics, (4), pp. 2807-2816, [Article]
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.
| Item Type: | Article |
|---|---|
| Erschienen: | 1991 |
| Creators: | Albrecht, T. and Elben, H. and Jäger, R. and Kimmig, M. and Steiner, R. and Strobl, G. and Stühn, B. and Schwickert, H. and Ritter, C. |
| Title: | Molecular dynamics in perfluoro-n-eicosane. II. Components of disorder |
| Language: | English |
| 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. |
| Journal or Publication Title: | Journal of Chemical Physics |
| Volume: | 95 |
| Number: | 4 |
| Divisions: | 05 Department of Physics 05 Department of Physics > Institute for condensed matter physics |
| Date Deposited: | 26 Feb 2010 13:35 |
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