Temperature dependence of intramolecular disorder in the high-temperature phase of poly(tetrafluoroethylene) (phase I)

1988 ◽  
Vol 21 (4) ◽  
pp. 1174-1176 ◽  
Author(s):  
C. De Rosa ◽  
G. Guerra ◽  
V. Petraccone ◽  
R. Centore ◽  
P. Corradini
Keyword(s):  
High Temperature ◽  
Phase I ◽  
Temperature Dependence ◽  
High Temperature Phase ◽  
Temperature Phase

Disorder of (NH4)3H(SO4)2 in the high-temperature phase I

2011 ◽  
Vol 67 (2) ◽  
pp. 116-121 ◽  
Author(s):  
Yoo Jung Sohn ◽  
Karine M. Sparta ◽  
Martin Meven ◽  
Gernot Heger
Keyword(s):  
High Temperature ◽  
Hydrogen Bonds ◽  
Phase I ◽  
Careful Consideration ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Atom Model ◽  
Disordered Crystal ◽  
Proton Migration ◽  
Atom Position

The highly disordered crystal structure of triammonium hydrogen disulfate, (NH4)3H(SO4)2, in the high-temperature phase I was studied using single-crystal neutron diffraction. It is known that the O atom involved in hydrogen bonding between neighbouring SO4 tetrahedra is disordered and takes a split-atom position, building a two-dimensional hydrogen-bond network in the (001) plane. The H atoms in these SO4–H—SO4 hydrogen bonds are disordered and hence refined with a split-atom model. Moreover, from the much larger anisotropic mean-square displacements of ammonium protons the NH_4^+ groups were refined with a reasonable split-atom model, and their motional behaviour was also analysed by rigid-body treatment. Finally, careful consideration was given to show possible supplementary proton migration between the ammonium protons and those of the hydrogen bonds in this high-temperature phase.

35Cl NQR and Structural Studies of Chloroacetanilides C6H3Cl2NHCOCH3-xClx, 1 ≤ x ≤ 3

1992 ◽  
Vol 47 (1-2) ◽  
pp. 160-170
Author(s):  
Dirk Groke ◽  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Phenyl Group ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Chlorine Atoms ◽  
Space Group ◽  
Low Temperature Phase

AbstractThe temperature dependence of 35Cl NQR frequencies and the phase transition behaviour of chloroacetanilides (N-[2,6-dichlorophenyl]-2-chloroacetamide, -2,2-dichloroacetamide, -2,2,2-trichloroacetamide) were investigated. The crystal structure determination of N-[2,6-dichlorophenyl]- 2-chloroacetamide leads to the following: a = 1893.8 pm, b = 1110.7 pm, c = 472.1 pm, space group P212121 = D24 with Z = 4 molecules per unit cell. The arrangement of the molecules and their geometry is comparable to the high temperature phase of the acetyl compound N-[2,6-dichlorophenyl]- acetamide. For N-[2,6-diclorophenyl]-2,2,2-trichloroacetamide it was found: a = 1016.6 pm, b = 1194.3 pm, c = 1006.7 pm, ß= 101.79°, space group P21/c = C52h, Z = 4. The structure is similar to the low temperature phase of N-[2,6-dichlorophenyl]-acetamide. Parallelism between the temperature dependence of the 35C1 NQR lines of the CCl3 group and the X-ray diffraction results concerning the different behaviour of the chlorine atoms was observed. The structures of the compounds show intermolecular hydrogen bonding of the N - H • • • O - C type. The phenyl group and the HNCO function are nearly planar. A bleaching out of several 35Cl NQR lines at a temperature far below the melting point of the substances was observed. The different types of chlorine atoms (aromatic, chloromethyl) can be distinguished by their temperature coefficients of the 35Cl NQR frequencies. All the resonances found show normal "Bayer" temperature behaviour. N-[2,6-dichlorophenyl]-2,2-diehloroacetamide shows several solid phases. One stable low temperature phase and an instable high temperature phase (at room temperature) were observed. The different phases were detected by means of 35Cl NQR spectroscopy and thermal analysis

Ab initio structure determination of the high-temperature phase of anhydrous caffeine by X-ray powder diffraction

2005 ◽  
Vol 61 (3) ◽  
pp. 329-334 ◽  
Author(s):  
Patrick Derollez ◽  
Natália T. Correia ◽  
Florence Danède ◽  
Frédéric Capet ◽  
Frédéric Affouard ◽  
...  
Keyword(s):  
High Temperature ◽  
Phase I ◽  
Metastable State ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
X Ray ◽  
Ab Initio Structure

The high-temperature phase I of anhydrous caffeine was obtained by heating and annealing the purified commercial form II at 450 K. This phase I can be maintained at low temperature in a metastable state. A powder X-ray diffraction pattern was recorded at 278 K with a laboratory diffractometer equipped with an INEL curved position-sensitive detector CPS120. Phase I is dynamically orientationally disordered (the so-called plastic phase). The Rietveld refinements were achieved with rigid-body constraints. It was assumed that on each site, a molecule can adopt three preferential orientations with equal occupation probability. Under a deep undercooling of phase I, below 250 K, the metastable state enters in a glassy crystal state.

Crystal Structure and NQR of Two Copper (I) Complexes of 4,6-Dimethylpyrimidine-2-thione

1994 ◽  
Vol 49 (1-2) ◽  
pp. 193-198 ◽  
Author(s):  
Sundara Ramaprabhu ◽  
Edwin A. C. Lucken ◽  
Gérald Bernardinelli
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Low Temperature ◽  
Phase Change ◽  
Temperature Dependence ◽  
High Temperature Phase ◽  
Symmetry Element ◽  
Temperature Phase ◽  
Crystallographic Study ◽  
Low Temperature Phase

Abstract The crystal structure and 63Cu NQR spectra of two neutral hexanuclear Cu(I) complexes of 4,6-dimethylpyrimidine-2-thione, (Hdmpt); [dmptCu]66CHCl3 (l) and [dmptCu]6C2H4Cl2 (2), are reported. The number and relative intensities of the NQR resonances are in agreement with the results of the crystallographic study. The temperature-dependence of the resonances reveals that both compounds undergo a phase-change in the temperature range 77 K -300 K, both of which may be associated with the loss of a symmetry-element present in the high-temperature phase. The 35Cl resonances of CHCl3 in 1 could be observed in the low-temperature phase but the corresponding resonances for C2H4Cl2 in 2 were not detected.

Phase Transitions in CsSnCl3 and CsPbBr3 An NMR and NQR Study

1991 ◽  
Vol 46 (4) ◽  
pp. 329-336 ◽  
Author(s):  
Surendra Sharma ◽  
Norbert Weiden ◽  
Alarich Weiss
Keyword(s):  
Phase Transitions ◽  
High Temperature ◽  
Phase I ◽  
Powder Diffraction ◽  
Perovskite Structure ◽  
Room Temperature ◽  
Monoclinic Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray

Abstract The phase transitions in CsSnCl3 and CsPbBr3 have been studied by X-ray powder diffraction, by 81Br-NQR and by 'H-, 119Sn-, and 113Cs-NMR. At room temperature in air CsSnCl3 forms a hydrate which can be dehydrated to the monoclinic phase II of CsSnCl3. The high temperature phase I has the Perovskite structure, as the X-ray and NMR experiments show. The three phases of CsPbBr3, known from literature, have been corroborated. The results are discussed in the framework of the group ABX3, A = alkalimetal ion, B = IV main group ion, and X = Halogen ion

scholarly journals Disorder of the (NH4)3H(SO4)2in the high-temperature phase I: single-crystal neutron diffraction

2010 ◽  
Vol 66 (a1) ◽  
pp. s279-s279 ◽  
Author(s):  
Yoo Jung Sohn ◽  
Karine Sparta ◽  
Sebastian Prinz ◽  
Martin Meven ◽  
Helmut Klapper ◽  
...  
Keyword(s):  
High Temperature ◽  
Neutron Diffraction ◽  
Phase I ◽  
Single Crystal ◽  
High Temperature Phase ◽  
Temperature Phase

Structural Study of TlH2PO4 and TlD2PO4 in the High Temperature Phase

1995 ◽  
Vol 5 (7) ◽  
pp. 763-769 ◽  
Author(s):  
S. Rios ◽  
W. Paulus ◽  
A. Cousson ◽  
M. Quilichini ◽  
G. Heger ◽  
...  
Keyword(s):  
High Temperature ◽  
Structural Study ◽  
High Temperature Phase ◽  
Temperature Phase

LATTICE DYNAMICS CALCULATIONS FOR SOLID BIPHENYL IN THE HIGH TEMPERATURE PHASE

1981 ◽  
Vol 42 (C6) ◽  
pp. C6-599-C6-601 ◽  
Author(s):  
T. Wasiutynski ◽  
I. Natkaniec ◽  
A. I. Belushkin
Keyword(s):  
High Temperature ◽  
Lattice Dynamics ◽  
High Temperature Phase ◽  
Temperature Phase
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