Molecular orientation in tetraiodoethylene single crystals

Thackeray, D. P. C.; Shirley, Robin; Oralratmanee, C.; Kipps, Michael; Stace, B. C.

doi:10.1016/0022-2860(74)85097-0

Cited by 4 publications

(2 citation statements)

References 4 publications

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“…Thus there are two orientations of this bond, and because the crystal potential would be little affected by the choice between these orientations, disorder between them is expected. Spectroscopic measurements by Thackeray, Shirley, Oralratmanee, Kipps & Stace (1974) with crystals at 300 K suggest that more molecules are aligned with the ethylenic bond nearly parallel to a*.…”

Section: Introduetlonmentioning

confidence: 96%

Disorder in crystalline tetraiodoethylene; constrained refinements of neutron powder diffraction data

Pawley¹

1978

Acta Crystallogr Sect B

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The 4 K results of Haywood & Shirley [Acta Cryst. (1977), B33, 1765-1773 have been reanalysed using the constrained-refinement program EDINP. The molecules are constrained to mmm symmetry and disorder is allowed on both molecular sites. One site is fully ordered, whereas the other is disordered to 21%. New roomtemperature results indicate disorder on both sites, but as certain unexplained features appear in the diffraction scan at this temperature, scans at intermediate temperatures are required before a satisfactory explanation can be found. The significance of the low-temperature result is thought to be high and a possible significance test is suggested.

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Section: Introduetlonmentioning

confidence: 96%

Disorder in crystalline tetraiodoethylene; constrained refinements of neutron powder diffraction data

Pawley¹

1978

Acta Crystallogr Sect B

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“…The lattice parameters have been measured together with interatomic distances, and the heavy-atom structure of Kitaigorodsky et al (1953) confirmed, showing that no major phase transition has occurred. It proved possible to locate the C atoms, and to show that in both molecules the C=C bonds are fully ordered in the solid at 4 K and aligned approximately along a*, as predicted by Thackeray et al (1974). Because of the high potential-energy barrier to molecular rotation, it is to be expected that the ordering will persist at room temperature.t…”

Section: Discussionmentioning

confidence: 98%

The structure of tetraiodoethylene at 4 K

Haywood¹,

Shirley²

1977

Acta Crystallogr Sect B

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The crystal and molecular structure of tetraiodoethylene (C214) at 4 K has been determined by neutron powder diffraction with Rietveld's profile-refinement method. Three independent data sets at different wavelengths were collected and used in the calculations. The measurements were sufficiently accurate to locate the C atoms in the molecules, and to show that the C=C bonds in both molecules are fully ordered and aligned approximately parallel to a*. The dimensions of the unit cell at 4 K and several interatomic distances are reported. The estimated standard deviations derived by this method are discussed and a normalization and weighting scheme for combining results from multiple power-data sets is suggested.1765

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