scholarly journals Studies of Structure and Phase Transition in [C(NH2)3]HgBr3 and [C(NH2)3]HgI3 by Means of Halogen NQR, 1H NMR, and Single Crystal X-Ray Diffraction

2000 ◽  
Vol 55 (1-2) ◽  
pp. 230-236 ◽  
Author(s):  
Hiromitsu Terao ◽  
Masao Hashimoto ◽  
Shinichi Hashimoto ◽  
Yoshihiro Furukawa
Keyword(s):  
Phase Transition ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Order ◽  
H Nmr ◽  
Trigonal Bipyramidal ◽  
Second Order Phase Transition

(TThe crystal structure of [C(NH2)3]HgBr3 was determined at room temperature: monoclinic, space group C2/c, Z = 4, a = 775.0(2), b = 1564.6(2), c = 772.7(2) pm, β = 109.12(2)°. In the crystal, almost planar HgBr3- ions are connected via Hg ··· Br bonds, resulting in single chains of trigonal bipyramidal HgBr5 units which run along the c direction. [C(NH2)3]HgI3 was found to be isomorphous with the bromide at room temperature. The temperature dependence of the halogen NQR frequencies (77 < 77K < ca. 380) and the DTA measurements evidenced no phase transition for the bromide, but a second-order phase transition at (251 ± 1) K (Tc1) and a first-order one at (210 ± 1) K for the iodide. The transitions at Tc2are accompanied with strong supercooling and significant superheating. The room temperature phase (RTP) and the intermediate temperature phase (ITP) of the iodide are characterized by two 127I(m=1/2↔3/2) NQR lines which are assigned to the terminal and the bridging I atoms, respectively. There exist three lines in the lowest temperature phase (LTP), indicating that the resonance line of the bridging atom splits into two. The signal intensities of the 127I(m =1/2↔3/2) NQR lines in the LTP decrease with decreasing temperature resulting in no detection below ca. 100 K. The 127I(m=1/2↔3/2) NQR frequency vs. temperature curves are continuous at Tcl, but they are unusual in the LTP. The T1vs. Tcurves of 1H NMR for the bromide and iodide are explainable by the reorientational motions of the cations about their pseudo three-fold axes. The estimated activation energies of the motions are 35.0 kJ/mol for the bromide, and 24.1, 30.1, and 23.0 kJ/mol for the RTP, FTP, and LTP of the iodide, respectively

Narrowing of the 35Cl NQR Lines of Trichloroacetamide Caused by Its Ferroelectric Phase Transition

1990 ◽  
Vol 45 (3-4) ◽  
pp. 327-333 ◽  
Author(s):  
Masao Hashimoto ◽  
Akiko Shono ◽  
Yoshiyuki Mido ◽  
Haruo Niki ◽  
Hiroshi Hentona ◽  
...  
Keyword(s):  
Phase Transition ◽  
Dielectric Behavior ◽  
High Temperature Phase ◽  
Monoclinic Space Group ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray ◽  
H Nmr ◽  
35Cl Nqr

Abstract Dielectric measurements on single crystals and DSC of the title compound (monoclinic, space group P21) revealed a ferroelectric transition at ca. 355 K (ΔH ≈ 0.5 kJ mol-1) Powder x-ray diffraction indicated that the high temperature phase is also monoclinic and the change in volume at the transition is very small. A displacement of hydrogen atoms is considered as responsible for the appearance of ferroelectricity. The 35Cl NQR signals at ca. 77 K were considerably broad, but a drastic narrowing took place after the compound had once experienced the phase transition. A tentative assignment of the NQR spectrum was made from a calculation of the NQR frequencies based on the CNDO/2 method. Another phase transition was evidenced by a small drift of the DSC curve and a slight anomaly of the dielectric behavior around 358 K. The present 1H NMR experiments gave no indication of the onset of torsional motion of the NH2 group reported to occur at ca. 210 K.

Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4

1990 ◽  
Vol 48 (4) ◽  
pp. 172-173
Author(s):  
Naoki Yamamoto ◽  
Makoto Kikuchi ◽  
Tooru Atake ◽  
Akihiro Hamano ◽  
Yasutoshi Saito
Keyword(s):  
Phase Transition ◽  
Electron Microscope Study ◽  
Room Temperature ◽  
Hexagonal Lattice ◽  
Ferroelectric Materials ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Periodic Arrays ◽  
Modulation Wave Vector

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.

Crystal Structure and Phase Transition of 4-Aminopyridinium Tetrabromoantimonate(III) as Studied by Bromine and Antimony NQR, Proton NMR, and Single Crystal X-Ray Diffraction

2000 ◽  
Vol 55 (1-2) ◽  
pp. 167-172 ◽  
Author(s):  
Masao Hashimoto ◽  
Shinichi Hashimoto ◽  
Hiromitsu Terao ◽  
Masayuki Kuma ◽  
Haruo Niki ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Monoclinic Space Group ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Reorientational Motion ◽  
H Nmr ◽  
Crystal Dynamics ◽  
Motional Narrowing ◽  
Low Temperature Phase

The crystal structure of the room temperature phase (RTP) of the title compound was determined at 297 K (monoclinic, space group C2/c, a = 1384.2(2), b = 1377.8(3), c = 755.5(2) pm, β = 121.58(1)°). A complicated disorder was found for the cation. A phase transition from the low-temperature phase (LTP) to the RTP was found at (224 ±1) K (Tc). The 1H NMR spectra showed a sharp motional narrowing at ca. T=Tc , indicating the occurrence of a reorientational motion of the cation in the RTP in accord with the disorder. It was found that another reorientational motion is excited in the LTP. Four 81Br NQR lines (132.71, 115.38, 61.54 and 59.31 MHz at 77 K) and two Sb NQR lines (53.78 and 33.76 MHz at 77 K) were found in the LTP, while a single 81Br NQR line was observed at T> 276 K (ca. 121.80 MHz at 300 K). Crystal dynamics are discussed on the basis of the temperature dependence of the NQR, 1H NMR line width, and 1H NMR T1.

The synthesis, and molecular and crystal structure of diphenyl(2-oxidonaphthylmethyl-iminoacetato)tin(IV)

1996 ◽  
Vol 74 (11) ◽  
pp. 2041-2047 ◽  
Author(s):  
Frank. E. Smith ◽  
Lian Ee Khoo ◽  
Ngoh Khang Goh ◽  
Rosemary C. Hynes ◽  
George Eng
Keyword(s):  
Crystal Structure ◽  
Elemental Analysis ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Trigonal Bipyramidal ◽  
Intermolecular Contacts ◽  
Distorted Trigonal Bipyramidal Coordination ◽  
Distorted Trigonal Bipyramidal

The new diorganotin complex ((C6H5)2Sn(OC10H6CH=NCH2COO)) was prepared and characterized by 1H NMR, IR, elemental analysis, and a single crystal X-ray diffraction study. The crystals are monoclinic, space group P21/a with a = 16.9167(9) Å, b = 19.1276(16) Å, c = 26.538(2) Å, β = 100.534(6)°, V = 8442.5(11) Å3, Z = 16, and Dcalc = 1.574 Mg m−3. The final discrepancy factors are RF = 0.030, and RW = 0.021 for 6524 significant reflections. The tin atom has a distorted trigonal bipyramidal coordination, with no short intermolecular contacts. The two axial Sn—O bonds of 2.12 Å and 2.09 Å and the equatorial Sn—N bond of 2.14 Å are among the shortest found in related complexes. Key words: diorganotin(IV), bicycloazastannoxide, trigonal bipyramidal, antitumour.

Powder Diffraction Data of Polymorphic Phases of Dicesium Cadmium Tetraiodide Cs2CdI4

1986 ◽  
Vol 1 (2) ◽  
pp. 35-36 ◽  
Author(s):  
V. Touchard ◽  
M. Louër ◽  
D. Louër
Keyword(s):  
Phase Transition ◽  
Thermal Analysis ◽  
Room Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Indexing Methods ◽  
X Ray ◽  
Two Phases

Introduction: Phase transition has been recently observed in Cs2CdI4 (Touchard, Louër, Auffrédic & Louër, 1986). Thermal analysis has shown that the transformation occurs at 122°C. By quenching, the high temperature phase (β) can be stabilized at room temperature. In the present work we report the X-ray diffraction powder data, at room temperature, for the two phases α- and β-Cs2CdI4. Both phases have been indexed automatically by using powder indexing methods.

Phase Diagram of the Orientationally Order-disorder Binary System 2,2-dimethyl-1,3-propanediol / 2,2-dimethyl-1,3-diaminopropane, [(CH3)2 C(CH2OH)2]x [(CH3)2C(CH2NH2)2]1-x · A Thermodynamic, X-ray, and 1H-NMR study

1996 ◽  
Vol 51 (7) ◽  
pp. 871-881 ◽  
Author(s):  
Roman Strauss ◽  
Sigmar Braun ◽  
Shi-qi Dou ◽  
Hartmut Fuess ◽  
Alarich Weiss
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Binary System ◽  
Phase I ◽  
1H Nmr ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Constants ◽  
H Nmr

AbstractThe phase diagram of the binary system [2,2-dimethyl-1,3-propanediol]x (1) / [2,2-dimethyl-1,3- diaminopropane]1-x (2) was studied by X-ray diffraction and DTA/DSC, for (2) also by 1H-NMR. The system is miscible over the whole concentration range 0 ≤ x ≤ 1 in the liquid state and in the plastic solid state, phase I, just below the melting point. At lower temperatures the system is demixing, and at room temperature two plastic mixed crystals coexist. The plastic phases of (1), (2), and (l)x(2)1-x crystallize face centered cubic, Fm3m, Z = 4, the lattice constants decreasing linearely with increasing x, and the lattice constants are: (1) a(327K) = 880.3 pm , (2) a(243K) = 905.6 pm. By single crystal X-ray diffraction the structure of the ordered phase II of (1) was refined at room temperature, monoclinic, P21/n, Z = 4, a = 596.9 pm, b = 1090.2 pm, c = 1011.0 pm, β = 99.74°. The results are in good agreement with the literature. The phase transition temperatures (in Kelvin) are T1→m = 399.2, TMm→1 = 399.7, T11→1 = 316.2, T1→11 = 308.2 for (1); = 300.2, = 301.7, T11→1 = 228.7, T1→n = 194.2 for (2). Strong hysteresis is observed for the transition T1→11 in (2). In the mixed systems (1)x(2)1-x, 0 < x < 1, the disordered phases do not order even by quenching to liquid nitrogen temperature. High resolution 1 H-NMR measurements are reported for phase I of (2) as a function of temperature. The “liquid” 1H-NMR spectrum is present far below the thermodynamic phase transition temperature T11-1, overlapping the wide line unresolved powder spectrum of phase II.

scholarly journals High-temperature phase transition of SrRuO3and SrHfO5: X-ray diffraction and PAC spectroscopy

1996 ◽  
Vol 52 (a1) ◽  
pp. C364-C364
Author(s):  
J. A. Guevara ◽  
S. L. Cuffini ◽  
Y. P. Mascarenhas ◽  
P. de la Presa ◽  
A. Ayala ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Pac Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Phase Transition

scholarly journals Исследование кинетики твердофазного перехода в тетракозане С-=SUB=-24-=/SUB=-Н-=SUB=-50-=/SUB=- методом высокоразрешающей синхротронной рентгеновской порошковой дифракции

2019 ◽  
Vol 61 (6) ◽  
pp. 1190
Author(s):  
B.A. Марихин ◽  
П.В. Дороватовский ◽  
Я.B. Зубавичус ◽  
M.B. Байдакова ◽  
E.M. Иванькова ◽  
...  
Keyword(s):  
Phase Transition ◽  
Small Angle ◽  
Diffuse Phase Transition ◽  
Basic Research ◽  
X Ray Diffraction ◽  
Kurchatov Institute ◽  
X Ray ◽  
First Order ◽  
Basic Research Project ◽  
Diffuse Phase

With the help of small angle X-ray diffraction using synchrotron X-ray beamline"Belok" in NRC «Kurchatov Institute» was shown that the first order sold phase transition in the tetracosane C24H50 develops by a heterogeneous mechanism in a very narrow thermal interval (delta ≈0,1K ) in accordance with the theory of diffuse phase transition. The work was financially supported by the Presidium RAN Program №32 "Nanostructures: physics, chemistry, biology, basics of technology" and Russian Foundation of Basic Research (project 16-03-00493А) using beamline "Belok" in NRC

scholarly journals The Isomorphous Structures of Ammonium trans-Diiodobis(ethanedial-dioximato-(1–)-N,N′)cobaltate(III) and Ammonium trans-Diiodobis(ethanedial-dioximato-(1–)-N,N′)rhodate(III): Extended Metaloximate Chains with a Novel ···I–M–I···I–M–I··· Zigzagged Structure

1990 ◽  
Vol 45 (11) ◽  
pp. 1508-1512 ◽  
Author(s):  
Michel Mégnamisi-Bélombé ◽  
Bernhard Nuber
Keyword(s):  
Room Temperature ◽  
Ammonium Salts ◽  
Monoclinic Space Group ◽  
Hydroxyl Groups ◽  
Coordination Geometry ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anionic Complexes ◽  
Complex Anions

The ammonium salts of the complex anions trans-diiodobis(ethanedial-dioximato)-cobaltate(III), [Col2(GH)2]-, and trans-diiodobis(ethanedial-dioximato)rhodate(III), [RhI2(GH)2]- (GH- = ethanedial dioximate or glyoximate), have been synthesized and their structures determined from single crystal X-ray diffraction data at room temperature. The crystals of the two salts are monoclinic, space group C2/c. NH4[CoI2(GH)2] (I) crystallizes as dark-brown prisms with a greenish reflectance; its crystal data are: C4H10Col2N5O4, Mr = 504.90; a = 8.910(6), b = 11.700(9), c = 11.691(6) Å; β = 93.55(5)°; V = 1216.4 Å3; Z = 4; Dc = 2.78 Mg m-3. NH4[RhI2(GH)2] (II) crystallizes as yellow-brown blocks with crystal data: C4H10I2N5O4Rh, Mr = 548.88; a = 9.038(4), b = 11.949(5), c = 11.770(3) Å; β = 95.54(3)°; V = 1265.16 A3; Z = 4; Dc = 2.87 Mg m-3. The two structures were refined to a final RW = 0.045 for 1209 observed independent reflections and 95 parameters for I, and to a final RW = 0.040 for 1922 observed independent reflections and 87 parameters for II. The coordination geometry around Co or Rh in the anionic complexes is a distorted (4 + 2) octahedron of four equatorial chelating N atoms and two apical iodides. The H atoms of the hydroxyl groups are involved, as usual, in intramolecular O—H—O bridges with uniform Ο···Ο separations of 2.582 Å for I, and 2.713 Å for II. The rectilinear I—Co—I or I—Rh—I triads form “infinite” zigzag chains extending parallel to the ab plane, with a weak I—I contact of 3.988 Å for I, and 4.010 Å for II.

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