Temperature-induced reversible structural phase transition and X-ray diffuse scattering in 2-amino-3-nitropyridinium hydrogen sulfate

2017 ◽  
Vol 73 (3) ◽  
pp. 337-346 ◽  
Author(s):  
Tamara J. Bednarchuk ◽  
Dorota Kowalska ◽  
Vasyl Kinzhybalo ◽  
Marek Wołcyrz
Keyword(s):  
Phase Transition ◽  
Phase I ◽  
Phase Ii ◽  
Diffuse Scattering ◽  
Structural Phase ◽  
Type Model ◽  
Hydrogen Sulfate ◽  
Space Group ◽  
X Ray ◽  
Reversible Phase Transition

The novel polar material 2-amino-3-nitropyridinium hydrogen sulfate, C5H6N3O2(HSO4) (abbreviated as 2A3NP-HS), was obtained and structurally characterized by means of single-crystal X-ray diffraction. At room temperature, 2A3NP-HS crystallizes as a non-centrosymmetric disordered phase (I) in the orthorhombicPna21space group. On cooling below 298 K, 2A3NP-HS undergoes a reversible phase transition to phase (II) with the monoclinic non-centrosymmetricP21space group. This transition might be classified as an `order–disorder' type. The structural details in both phases are analysed. Additionally, for phase (I), in the 304–365 K temperature range, diffuse scattering was found to be present in the form of elongated streaks parallel to thea* direction. This can be unravelled when implementing a short-range order affecting anionic cationic ribbons occurring in the structure, with correlations acting both in thea-direction and in thebc-plane. The results of Monte Carlo simulations, adapting a two-dimensional Ising-type model, reveal the formation of domains, which areb-elongated and thin alonga. Locally, the stacking of the ribbons in the domains reflects the ordered arrangement observed in the low-temperature monoclinic phase (II).

Synchrotron X-ray diffuse scattering from a stable polymorphic material: terephthalic acid, C8H6O4

2017 ◽  
Vol 73 (1) ◽  
pp. 112-121 ◽  
Author(s):  
D. J. Goossens ◽  
E. J. Chan
Keyword(s):  
Phase Transition ◽  
Terephthalic Acid ◽  
Diffuse Scattering ◽  
Structural Phase ◽  
Local Order ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Harmonic Model ◽  
X Ray ◽  
Polymorphic Materials

Terephthalic acid (TPA, C8H6O4) is an industrially important chemical, one that shows polymorphism and disorder. Three polymorphs are known, two triclinic [(I) and (II)] and one monoclinic (III). Of the two triclinic polymorphs, (II) has been shown to be more stable in ambient conditions. This paper presents models of the local order of polymorphs (I) and (II), and compares the single-crystal diffuse scattering (SCDS) computed from the models with that observed from real crystals. TPA shows relatively weak and less-structured diffuse scattering than some other polymorphic materials, but it does appear that the SCDS is less well modelled by a purely harmonic model in polymorph (I) than in polymorph (II), according to the idea that the diffuse scattering is sensitive to anharmonicity that presages a structural phase transition. The work here verifies that displacive correlations are strong along the molecular chains and weak laterally, and that it is not necessary to allow the —COOH groups to librate to successfully model the diffuse scattering – keeping in mind that the data are from X-ray diffraction and not directly sensitive to H atoms.

Space-Group Determination of the Orthorhombic Form of NaV6O11

1995 ◽  
Vol 28 (5) ◽  
pp. 599-603 ◽  
Author(s):  
Y. Kanke ◽  
H. Shigematsu ◽  
K. Ohshima ◽  
K. Kato
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Single Crystal ◽  
Diffraction Study ◽  
Structural Phase ◽  
Unit Cell ◽  
Single Crystal Diffraction ◽  
Space Group ◽  
X Ray

The unit cell and space group of orthorhombic NaV6O11 (low-temperature form) are found by an X-ray single-crystal diffraction study at 300 K (hexagonal, P63/mmc), 100 K (hexagonal, P63 mc) and 20 K (orthorhombic). The orthorhombic form (o) shows no superstructure and its unit cell is related to the hexagonal one (h): a o ≃ a h + b h , a o ≃ −a h + b h and c o ≃ c h . Bijvoet-pair examination confirms that it crystallizes in the noncentrosymmetric space group Cmc21. The hexagonal (P63 mc)-orthorhombic (Cmc21) structural phase transition is proved to be of second order.

Reversible structural phase transition of pyridinium-4-carboxylic acid perchlorate

2010 ◽  
Vol 43 (5) ◽  
pp. 1031-1035 ◽  
Author(s):  
Heng-Yun Ye ◽  
Hong-Ling Cai ◽  
Jia-Zeng Ge ◽  
Ren-Gen Xiong
Keyword(s):  
Phase Transition ◽  
Carboxylic Acid ◽  
Structural Phase ◽  
Differential Scanning Calorimetry Measurement ◽  
Scanning Calorimetry ◽  
Reflection Index ◽  
Space Group ◽  
Cell Parameters ◽  
Bonding Effect ◽  
Reversible Phase Transition

Pyridinium-4-carboxylic acid perchlorate (C6H6NO2·ClO4) was synthesized and separated as crystals. Differential scanning calorimetry measurement shows that this compound undergoes a reversible phase transition at about 122 K with a heat hysteresis of 1.8 K. A dielectric anomaly observed at 127 K further confirms the phase transition. The low-temperature (LT;T= 103 K) structure has space groupP21/cand cell parametersa= 17.356 (6),b= 13.241 (3),c= 16.161 (7) Å, β = 138.055 (17)°. The high-temperature (HT;T= 298 K) structure has space groupP21/cand cell parametersa= 5.5046 (11),b= 13.574 (3),c= 11.834 (2) Å, β = 99.35 (3)°, but can be re-described using new axesa′ =a,b′ =b,c′ = −2a+c,V′ =Vto give the cella′ = 5.5046 (11),b′ = 13.574 (3),c′ = 17.424 (3) Å, β′ = 137.92 (3)° and space groupP21/c. The associated coordinate transformation isx′ =x+ 2z,y′ =y,z′ =zand the associated reflection index transformation ish′ =h,k′ =k,l′ =l− 2h. The relationship between the two cells is 3a,b,c(HT) approximatesa,b,c(LT). The crystal comprises one-dimensional hydrogen-bonded chains of the pyridinium-4-carboxylic acid cations and perchlorate anions. A precise analysis of the main packing and structural differences as well as the changes in the intermolecular interactions between the HT phase and the LT phase reveals that the disorder–order transition of the perchlorate anions may be the driving force of the transition, and the hydrogen-bonding effect may contribute to the transition as a secondary parameter.

scholarly journals Pressure-induced coherent sliding-layer transition in the excitonic insulator Ta2NiSe5

IUCrJ ◽  
2018 ◽  
Vol 5 (2) ◽  
pp. 158-165 ◽  
Author(s):  
Akitoshi Nakano ◽  
Kento Sugawara ◽  
Shinya Tamura ◽  
Naoyuki Katayama ◽  
Kazuyuki Matsubayashi ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase I ◽  
Phase Ii ◽  
Ambient Pressure ◽  
Structural Phase ◽  
Orthorhombic Phase ◽  
Phase Iii ◽  
Layer Transition ◽  
Coulombic Interactions ◽  
Excitonic Insulator

The crystal structure of the excitonic insulator Ta2NiSe5has been investigated under a range of pressures, as determined by the complementary analysis of both single-crystal and powder synchrotron X-ray diffraction measurements. The monoclinic ambient-pressure excitonic insulator phase II transforms upon warming or under a modest pressure to give the semiconductingC-centred orthorhombic phase I. At higher pressures (i.e.>3 GPa), transformation to the primitive orthorhombic semimetal phase III occurs. This transformation from phase I to phase III is a pressure-induced first-order phase transition, which takes place through coherent sliding between weakly coupled layers. This structural phase transition is significantly influenced by Coulombic interactions in the geometric arrangement between interlayer Se ions. Furthermore, upon cooling, phase III transforms into the monoclinic phase IV, which is analogous to the excitonic insulator phase II. Finally, the excitonic interactions appear to be retained despite the observed layer sliding transition.

scholarly journals Inorganic Anion Regulates the Phase Transition in Two Organic Cation Salts Containing [(4-Nitroanilinium)(18-crown-6)]+ Supramolecules

2017 ◽  
Author(s):  
Yuan Chen ◽  
Yang Liu ◽  
Binzu Gao ◽  
Chuli Zhu ◽  
Zunqi Liu
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Variable Temperature ◽  
Structural Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Space Group ◽  
X Ray

Two novel inorganic–organic hybrid supramolecular assemblies, namely, (4-HNA)(18-crown-6)(HSO4) (1) and (4-HNA)2(18-crown-6)2(PF6)2(CH3OH) (2) (4-HNA = 4-nitroanilinium), were synthesized and characterized by infrared spectroscopy, single X-ray diffraction, differential scanning calorimetry (DSC), and temperature-dependent dielectric measurements. The two compounds underwent reversible phase transitions at about 255 K and 265 K, respectively. These phase transitions were revealed and confirmed by the thermal anomalies in DSC measurements and abrupt dielectric anomalies during heating. The phase transition may have originated from the [(4-HNA)(18-crown-6)]+ supramolecular cation. The inorganic anions tuned the crystal packings and thus influenced the phase-transition points and types. The variable-temperature X-ray diffraction data for crystal 1 revealed the occurrence of a phase transition in the high-temperature phase with the space group of P21/c and in the low-temperature phase with the space group of P21/n. Crystal 2 exhibited the same space group P21/c at different temperatures. The results indicated that crystals 1 and 2 both underwent an iso-structural phase transition.

scholarly journals High-Pressure Behaviors of Ag2S Nanosheets: An in Situ High-Pressure X-Ray Diffraction Research

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1640
Author(s):  
Ran Liu ◽  
Bo Liu ◽  
Quan-Jun Li ◽  
Bing-Bing Liu
Keyword(s):  
High Pressure ◽  
Phase I ◽  
Phase Ii ◽  
Structural Phase ◽  
Phase Iii ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Phase ◽  
Ag2s Nanoparticles

An in situ high-pressure X-ray diffraction study was performed on Ag2S nanosheets, with an average lateral size of 29 nm and a relatively thin thickness. Based on the experimental data, we demonstrated that under high pressure, the samples experienced two different high-pressure structural phase transitions up to 29.4 GPa: from monoclinic P21/n structure (phase I, α-Ag2S) to orthorhombic P212121 structure (phase II) at 8.9 GPa and then to monoclinic P21/n structure (phase III) at 12.4 GPa. The critical phase transition pressures for phase II and phase III are approximately 2–3 GPa higher than that of 30 nm Ag2S nanoparticles and bulk materials. Additionally, phase III was stable up to the highest pressure of 29.4 GPa. Bulk moduli of Ag2S nanosheets were obtained as 73(6) GPa for phase I and 141(4) GPa for phase III, which indicate that the samples are more difficult to compress than their bulk counterparts and some other reported Ag2S nanoparticles. Further analysis suggested that the nanosize effect arising from the smaller thickness of Ag2S nanosheets restricts the relative position slip of the interlayer atoms during the compression, which leads to the enhancing of phase stabilities and the elevating of bulk moduli.

An unprecedented structural phase transition in struvite-type compounds: dimorphism of KMgAsO4(H2O)6

2019 ◽  
Vol 74 (1) ◽  
pp. 9-14
Author(s):  
Matthias Weil
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Diffraction Data ◽  
Structural Changes ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Continuous Type ◽  
Reversible Phase Transition

AbstractThe crystal structure of struvite-type KMgAsO4(H2O)6 has been redetermined from single crystal X-ray diffraction data at room temperature. The previous structure model based on powder X-ray diffraction data was confirmed with higher precision and accuracy and with all hydrogen atoms located. KMgAsO4(H2O)6 undergoes a reversible phase transition of the continuous type at 263(2) K, changing the symmetry from orthorhombic to monoclinic. The corresponding Pnm21→P1121 symmetry reduction is of a translationengleiche type with index 2 and was monitored by temperature-dependent powder X-ray diffraction measurements. Such a phase transition is unprecedented for struvite-type compounds. The crystal structure of the monoclinic polymorph was determined from a two-domain crystal at 100 K. Except for the motion of one of the water molecules towards stronger hydrogen-bonding interactions, structural changes between the two polymorphs are small.

Crystal structure and structural phase transition in bismuth-containing HoFe3(BO3)4 in the temperature range 11–500 K

2019 ◽  
Vol 75 (6) ◽  
pp. 954-968 ◽  
Author(s):  
Ekaterina S. Smirnova ◽  
Olga A. Alekseeva ◽  
Alexander P. Dudka ◽  
Dmitry N. Khmelenin ◽  
Kirill V. Frolov ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Local Environment ◽  
Atomic Displacement ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Atomic Displacement Parameters ◽  
Thermal Vibrations

An accurate single-crystal X-ray diffraction study of bismuth-containing HoFe3(BO3)4 between 11 and 500 K has revealed structural phase transition at T str = 365 K. The Bi atoms enter the composition from Bi2Mo3O12-based flux during crystal growth and significantly affect T str. The content of Bi was estimated by two independent methods, establishing the composition as (Ho0.96Bi0.04)Fe3(BO3)4. In the low-temperature (LT) phase below T str the (Ho0.96Bi0.04)Fe3(BO3)4 crystal symmetry is trigonal, of space group P3121, whereas at high temperature (HT) above 365 K the symmetry increases to space group R32. There is a sharp jump of oxygen O1 (LT) and O2 (LT) atomic displacement parameters (ADP) at T str. O1 and O2 ADP ellipsoids are the most elongated over 90–500 K. In space group R32 specific distances decrease steadily or do not change with decreasing temperature. In space group P3121 the distortion of the polyhedra Ho(Bi)O6, Fe1O6 and Fe2O6, B2O3 and B3O3 increases with decreasing temperature, whereas the triangles B1O3 remain almost equilateral. All BO3 triangles deviate from the ab plane with decreasing temperature. Fe–Fe distances in Fe1 chains decrease, while distances in Fe2 chains increase with decreasing temperature. The Mössbauer study confirms that the FeO6 octahedra undergo complex dynamic distortions. However, all observed distortions are rather small, and the general change in symmetry during the structural phase transition has very little influence on the local environment of iron in oxygen octahedra. The Mössbauer spectra do not distinguish two structurally different Fe1 and Fe2 positions in the LT phase. The characteristic temperatures of cation thermal vibrations were calculated using X-ray diffraction and Mössbauer data.

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