Neutron diffraction study of the plastic phases of polycrystalline SF<sub>6</sub>and CBr<sub>4</sub>

Dolling, G.; Powell, B. M.; Sears, V. F.

doi:10.1080/00268977900101381

Cited by 126 publications

(119 citation statements)

References 34 publications

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“…There are two different crystalline phases of SF 6 at ambient pressure and low temperatures [2]. Between 90 K and 230 K SF 6 crystallises in a so-called "plastic" phase in a body-centred cubic (bcc) structure with space group Im3m and Z = 2 (one molecule per lattice point) [3]. In the "plastic" phase the molecules are orientationally disordered.…”

Section: Introductionmentioning

confidence: 99%

High-pressure phases of SF6 up to 32GPa from X-ray diffraction and Raman spectroscopy

Rademacher

Friedrich

Morgenroth

et al. 2015

Journal of Physics and Chemistry of Solids

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X-ray diffraction and Raman spectroscopy were employed to study the phase diagram of SF 6 at pressures up to 32 GPa. The known phase transformation of SF 6 phase I to phase II at around 2 GPa was confirmed. Discontinuities in the pressure dependence of the Raman frequencies and positions of X-ray reflections indicate further phase transitions at 10(1) and 19(1) GPa.The crystal structures of phases I and II were determined using single crystal X-ray diffraction. The structure of phase I corresponds to the "plastic" body-centred cubic low-temperature structure and the structure of phase II to the ordered monoclinic low-temperature structure. The bulk moduli of phase I and II were determined to be B 0,I = 6.3(2) GPa with B ′ I = 4 (fixed) and B 0,II = 8.5(8) GPa with B ′ II = 7.4(9), respectively. The linear compressibilities of phase II showed a slight anisotropy, which can be rationalised by consideration of the packing of the SF 6 molecules.

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Section: Introductionmentioning

confidence: 99%

High-pressure phases of SF6 up to 32GPa from X-ray diffraction and Raman spectroscopy

Rademacher

Friedrich

Morgenroth

et al. 2015

Journal of Physics and Chemistry of Solids

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“…The scientic interest has been mainly concentrated on the plastic crystalline phase, where the molecules possess higher symmetry than their lattice site symmetry 6 . Fullling the crystallographic site symmetry in time average, the molecules become rotating 3 .…”

Section: Introductionmentioning

confidence: 99%

“…Liquid diraction data was rst published in 1979 6 ; the rst discussion appeared only in 1997 20 , based on Reverse Monte Carlo 21 (RMC) structural modelling. The authors found that, in their system of rigid molecules, both molecular center molecular center and bromine atom bromine atom correlations resemble to those present in a closely packed structure.…”

Section: Introductionmentioning

confidence: 99%

“…the thermal resistivity is almost as large as in the liquid state, showing that the mean free path of elastic waves become short 4 . At the microscopic level, structural and dynamic properties have been studied extensively using (powder 6,7 , single crystal 3,8,9 ) diraction and triple-axis spectrometry 8,10,11 . Numerous models 3,615 have been invented for describing the scattering pattern from this phase, taking into account more and more detailed eects as computer power has been increasing.…”

Section: Introductionmentioning

confidence: 99%

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Local order and orientational correlations in liquid and crystalline phases of carbon tetrabromide from neutron powder diffraction measurements

Temleitner

Pusztai

2010

Phys. Rev. B

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(2008)). The BrBr partial radial distribution functions of the liquid and plastic crystalline phases are almost the same, while CC correlations clearly display long range ordering in the latter phase. Orientational correlations also suggest strong similarities between liquid and plastic crystalline phases, whereas the monoclinic phase behaves very dierently. Orientations of the molecules are distinct in the ordered phase, whereas in the plastic crystal their distribution seems to be isotropic.

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“…This scattering is proportional to the probability (Ix). If we neglect correlation effects between the orientation and the centre-of-mass deviation of an individual molecule then we can write lol of (5) as (Dolling, Powell & Sears, 1979) Im = IRl(l'~) + l~,l(ll, U) …”

Section: The Single-molecule Scatteringmentioning

confidence: 99%

Short-range-order correlations in the orientationally disordered phase of hexachloroethane. I. Diffuse X-ray scattering

Gerlach¹,

Prandl²

1988

Acta Cryst Sect A

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Diffuse X-ray scattering has been measured in the orientationally disordered phase of C2C16 at 453 K. A model structure, which was generated in a Monte Carlo program, reproduces the dominant singlemolecule part of the diffuse scattering. In addition the existence of a one-dimensional orientational order along the body diagonals ofthe cubic lattice is demonstrated. The related planes of diffuse scattering are calculated in terms of the Naya model [Naya (1974).

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Neutron diffraction study of the plastic phases of polycrystalline SF₆and CBr₄

Cited by 126 publications

References 34 publications

High-pressure phases of SF6 up to 32GPa from X-ray diffraction and Raman spectroscopy

High-pressure phases of SF6 up to 32GPa from X-ray diffraction and Raman spectroscopy

Local order and orientational correlations in liquid and crystalline phases of carbon tetrabromide from neutron powder diffraction measurements

Short-range-order correlations in the orientationally disordered phase of hexachloroethane. I. Diffuse X-ray scattering

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Neutron diffraction study of the plastic phases of polycrystalline SF6and CBr4

Cited by 126 publications

References 34 publications

High-pressure phases of SF6 up to 32GPa from X-ray diffraction and Raman spectroscopy

High-pressure phases of SF6 up to 32GPa from X-ray diffraction and Raman spectroscopy

Local order and orientational correlations in liquid and crystalline phases of carbon tetrabromide from neutron powder diffraction measurements

Short-range-order correlations in the orientationally disordered phase of hexachloroethane. I. Diffuse X-ray scattering

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Neutron diffraction study of the plastic phases of polycrystalline SF₆and CBr₄