On the Order-Disorder Phase Transition of Anilinium Halides. Crystal Structure of the High and Low Temperature Phase of Anilinium Iodide, C6H5NH ⊕3I⊖ (C6D5NH ⊕3I−). X-Ray and Neutron Diffraction Studies

1986 ◽  
Vol 90 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Gerhard Fecher ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Low Temperature ◽  
Neutron Diffraction ◽  
Temperature Phase ◽  
X Ray ◽  
Disorder Phase Transition ◽  
Low Temperature Phase

On the Phase Transition of Bis(pyridinium)hexachlorometallates, (C5H5NH)2[MCl6], M = Sn, Te, Pb, Pt. An X-Ray and 35Cl NQR Study

1987 ◽  
Vol 42 (7) ◽  
pp. 739-748 ◽  
Author(s):  
Dirk Borchers ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Phase Ii ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray ◽  
Lattice Constants ◽  
Pyridinium Ring ◽  
35Cl Nqr ◽  
Low Temperature Phase

A phase transition has been observed in bis(pyridinium) hexachlorometallates (C5H5NH)2[MIVCl6]. M = Sn. Te. Pb. Pt. The crystal structure of the low temperature phase II of the salt with M = Sn was determined, space group C 1ḷ- P 1̅, Z = 1 (a = 734.1pm, b = 799.0 pm, c = 799.7 pm,α= 83.229°. β = 65.377°, γ= 84.387°, T = 297 K). The four compounds are isotypic in phase II as well as in the high temperature phase I (C2H2-B2 /m, Z = 2) for which the crystal structure is known for M = Te . The lattice constants of all compounds (both phases) are given. The temperature dependence of the 35Cl NQR spectrum was investigated. The three line 35Cl NQR spectrum is in agreement with the crystal structure. The dynamics of the pyridinium ring shows up in a fade out of part of the 35Cl NQR spectrum . The influence o f H ↔ D exchange on 35Cl NQR is studied and an assignment of ν (35Cl) ↔ Cl(i) is proposed. The nature of the phase transition P1̅ (Z = 1) ↔ B2 /m (Z = 2) is discussed.

On the Order-Disorder Phase Transformation of Anilinium Halides.

1981 ◽  
Vol 36 (9) ◽  
pp. 967-974 ◽  
Author(s):  
Gerhard Fecher ◽  
Alarich Weiss ◽  
Gernot Heger
Keyword(s):  
Crystal Structure ◽  
Phase Transformation ◽  
High Temperature ◽  
Low Temperature ◽  
Neutron Diffraction ◽  
Temperature Phase ◽  
Ordered Structure ◽  
Low Temperature Phase

Abstract The crystal structure of the low temperature phase of anilinium bromide, C6H5NH3⊕Br⊖, was studied by neutron diffraction at T = 100 K. The refinement supports an ordered structure. The structures of the low and high temperature phases are compared and the mechanism of the phase transformation is discussed.

Atomic and domain structure of the low-temperature phase of barium metagermanate (BaGeO3)

2006 ◽  
Vol 62 (6) ◽  
pp. 1002-1009 ◽  
Author(s):  
Daniel Maria Többens ◽  
Volker Kahlenberg ◽  
Christian Gspan ◽  
Gerald Kothleitner
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Diffuse Scattering ◽  
Stacking Faults ◽  
Temperature Phase ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Positional Disorder ◽  
Low Temperature Phase ◽  
Xrpd Pattern

The crystal structure of the low-temperature form of barium metagermanate (BaGeO3) has been determined from laboratory X-ray powder diffraction data collected at 298.5 (5) K. The structure was found to consist of alternating layers of Ba cations and [GeO3]3 rings, and is closely related to pseudo-wollastonite. The rings show a twofold positional disorder owing to stacking faults. The stacking is not random, but can be rationalized by a twinning mechanism mapping the two non-congruent enantiomorphic polytypes of the structure onto each other. This model also explains the diffuse scattering and twinning observed in SAED and HRTEM, as well as the size and strain-like broadening effects found in the XRPD pattern.

X-ray diffraction study of the phase transition of K2Mn2(BeF4)3: a new type of low-temperature structure for langbeinites

2001 ◽  
Vol 57 (3) ◽  
pp. 221-230 ◽  
Author(s):  
A. Guelylah ◽  
G. Madariaga ◽  
V. Petricek ◽  
T. Breczewski ◽  
M. I. Aroyo ◽  
...  
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Mode Analysis ◽  
Cubic Phase ◽  
Temperature Phase ◽  
Temperature Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
New Type ◽  
Low Temperature Phase

The potassium manganese tetrafluoroberyllate langbeinite compound has been studied in the temperature range 100–300 K. Using DSC measurements, a phase transition has been detected at 213 K. The space group of the low-temperature phase was determined to be P1121 using X-ray diffraction experiments and optical observations of the domain structure. The b axis is doubled with respect to the prototypic P213 cubic phase. Lattice parameters were determined by powder diffraction data [a = 10.0690 (8), b = 20.136 (2), c = 10.0329 (4) Å, γ = 90.01 (1)°]. A precise analysis of the BeF4 tetrahedra in the low-temperature phase shows that two independent tetrahedra rotate in opposite directions along the doubled crystallographic axis. A symmetry mode analysis of the monoclinic distortion is also reported. This is the first report of the existence of such a phase transition in K2Mn2(BeF4)3 and also of a new type of low-temperature structure for langbeinite compounds.

Low temperature phase transition and crystal structure of CsMgPO4

2015 ◽  
Vol 221 ◽  
pp. 224-229 ◽  
Author(s):  
Maria Orlova ◽  
Sergey Khainakov ◽  
Dmitriy Michailov ◽  
Lukas Perfler ◽  
Christoph Langes ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Low Temperature ◽  
Temperature Phase ◽  
Temperature Phase Transition ◽  
Low Temperature Phase
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