Abstract
Perfluoro-n-eicosane (n-C20F42) passes through three different solid modifications, called M(T<146 K), I(146<T<200 K), and R(T>200 K). Structures of the phases M and R were characterized by x-ray scattering experiments. Crystals are built up by rectangular layers. In modification M layers are set up by arrays of right-handed and left-handed (15/7-) helices in alternate succession. The unit cell is monoclinic (a=9.65 Å, b=5.70 Å, c=28.3 Å, and β=97°; space group Pa). In modification R molecules are highly mobile. There is no ordering with regard to the helix handedness. Molecules resemble cylindrical objects and are packed in a hexagonal dense mode. Regular layer stacking results in crystals with rhombohedral symmetry (a=b=5.70 Å, c=85.00 Å, γ=120°; space group R3̄m).
References
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Dates
Type | When |
---|---|
Created | 23 years, 1 month ago (July 26, 2002, 8:38 a.m.) |
Deposited | 1 year, 6 months ago (Feb. 10, 2024, 8:20 a.m.) |
Indexed | 11 months, 3 weeks ago (Sept. 15, 2024, 2:30 a.m.) |
Issued | 34 years ago (Aug. 15, 1991) |
Published | 34 years ago (Aug. 15, 1991) |
Published Print | 34 years ago (Aug. 15, 1991) |
@article{Schwickert_1991, title={Molecular dynamics in perfluoro-n-eicosane. I. Solid phase behavior and crystal structures}, volume={95}, ISSN={1089-7690}, url={http://dx.doi.org/10.1063/1.460931}, DOI={10.1063/1.460931}, number={4}, journal={The Journal of Chemical Physics}, publisher={AIP Publishing}, author={Schwickert, Heinz and Strobl, Gert and Kimmig, Martin}, year={1991}, month=aug, pages={2800–2806} }