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.

Reversible phase transition of pyridinium-3-carboxylic acid perchlorate

2010 ◽  
Vol 66 (3) ◽  
pp. 387-395 ◽  
Author(s):  
Heng-Yun Ye ◽  
Li-Zhuang Chen ◽  
Ren-Gen Xiong
Keyword(s):  
Phase Transition ◽  
Carboxylic Acid ◽  
Relative Displacement ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
Cell Parameters ◽  
Dsc Measurements ◽  
Reversible Phase Transition ◽  
Reversible Phase ◽  
Hydrogen Bonded

Pyridinium-3-carboxylic acid perchlorate was synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurements show that this compound undergoes a reversible phase transition at ∼ 135 K with a wide hysteresis of 15 K. Dielectric measurements confirm the transition at ∼ 127 K. Measurement of the unit-cell parameters versus temperature shows that the values of the c axis and β angle change abruptly and remarkably at 129 (2) K, indicating that the system undergoes a first-order transition at T c = 129 K. The crystal structures determined at 103 and 298 K are all monoclinic in P21/c, showing that the phase transition is isosymmetric. The crystal contains one-dimensional hydrogen-bonded chains of the pyridinium-3-carboxylic acid cations, which are further linked to perchlorate anions by hydrogen bonds to form well separated infinite planar layers. The most distinct differences between the structures of the higher-temperature phase and the lower-temperature phase are the change of the distance between the adjacent pyridinium ring planes within the hydrogen-bonded chains and the relative displacement between the hydrogen-bonded layers. Structural analysis shows that the driving force of the transition is the reorientation of the pyridinium-3-carboxylic acid cations. The degree of order of the perchlorate anions may be a secondary order parameter.

A Reversible Non-disruptive Phase Transition Shown by the Zinc Iodide Dimethylformamide Complex ZnI2(dmf)2

1998 ◽  
Vol 54 (5) ◽  
pp. 663-670 ◽  
Author(s):  
R. A. Edwards ◽  
A. J. Easteal ◽  
O. P. Gladkikh ◽  
W. T. Robinson ◽  
M. M. Turnbull ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Intermolecular Forces ◽  
Scanning Calorimetry ◽  
Space Group ◽  
Cell Parameters ◽  
Reversible Phase Transition ◽  
Higher Temperature ◽  
High Temperature Form ◽  
Reversible Phase

At 228 K crystals of ZnI2(dmf)2 show a reversible phase transition which does not disrupt the lattice. Above the transition temperature the space group is C2/c and the cell contains eight symmetrically equivalent molecules. Cooling to below the transition temperature has little effect on the cell parameters or on the Zn- and I-atom positions, but the space group is now P21/n and the asymmetric unit comprises two conformationally different molecules. These arise from cooperative rotations of either ca +25 or −43° about the Zn—O bond of one of the dmf ligands in the high-temperature form. This displacive transition involves large movements of some atoms. The corresponding chloride and bromide are isomorphous with the higher temperature C2/c form, but it is only with the iodide that the weaker intermolecular forces permit the unusual phase change. The transition has been followed by differential scanning calorimetry, which gives an enthalpy change of 1.44 (5) kJ mol−1.

Temperature-induced first-order displacive phase transition of isonicotinamide-4-methoxybenzoic acid co-crystal

2017 ◽  
Vol 73 (2) ◽  
pp. 285-295 ◽  
Author(s):  
Tze Shyang Chia ◽  
Ching Kheng Quah
Keyword(s):  
Phase Transition ◽  
Single Crystal ◽  
Variable Temperature ◽  
Structural Phase ◽  
Differential Scanning Calorimetry Measurement ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
First Order ◽  
Displacive Phase Transition ◽  
Methoxybenzoic Acid

Isonicotinamide–4-methoxybenzoic acid co-crystal (1), C6H6N2O·C8H8O3, is formed through slow evaporation from methanol solution and it undergoes a first-order isosymmetry (monoclinicI2/a↔ monoclinicI2/a) structural phase transition atTc= 142.5 (5) K, which has been confirmed by an abrupt jump of crystallographic interaxial angle β from variable-temperature single-crystal XRD and small heat hysteresis (6.25 K) in differential scanning calorimetry measurement. The three-dimensional X-ray crystal structures of (1) at the low-temperature phase (LTP) (100, 140 and 142 K) and the high-temperature phase (HTP) (143, 150, 200, 250 and 300 K) were solved and refined as a simple non-disordered model with finalR[F2> 2σ(F2)] ≃ 0.05. The asymmetric unit of (1) consists of crystallographically independent 4-methoxybenzoic acid (A) and isonicotinamide (B) molecules in both enantiotropic phases. MoleculeAadopts a `near-hydroxyl' conformation in which the hydroxyl and methoxy groups are positioned on the same side. Both `near-hydroxyl' and `near-carbonyl' molecular conformations possess minimum conformational energies with an energy difference of < 0.15 kJ mol−1from a potential energy surface scan. In the crystal, molecules are joined into linearABBAarrays by intermolecular N—H...O and O—H...N hydrogen bonds which were preserved in both phases. However, theseABBAarrays are displaced from planarity upon LTP-to-HTP transition and the changes in inter-array interactions are observed in two-dimensional fingerprint plots of their Hirshfeld surfaces. ThePIXELenergies of each molecular pair in both phases were calculated to investigate the difference in intermolecular interaction energies before and after the displacement ofABBAarrays from planarity, which directly leads to the single-crystal-to-single-crystal phase transition of (1).

Structural evolution of a Ge-substituted SnSe thermoelectric material with low thermal conductivity

2018 ◽  
Vol 51 (2) ◽  
pp. 337-343 ◽  
Author(s):  
Federico Serrano-Sánchez ◽  
Norbert M. Nemes ◽  
José Luis Martínez ◽  
Oscar Juan-Dura ◽  
Marco Antonio de la Torre ◽  
...  
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Structural Evolution ◽  
Type Structure ◽  
Scanning Calorimetry ◽  
Space Group ◽  
Low Thermal Conductivity ◽  
Structure Space

Thermoelectric materials are expected to become new alternative sources of sustainable energy. Among them, the SnSe intermetallic alloy has been described as an excellent thermoelectric compound, characterized by an extremely low thermal conductivity with maximum performance at the onset of a structural phase transition at 800 K. Recently, novel SnSe derivatives with Ge substitution have been synthesized by a direct arc-melting technique. This produces nanostructured polycrystalline samples that exhibit a record high Seebeck coefficient, anticipating an excellent performance above room temperature. Here, the structural phase transition from a GeS-type structure (space groupPnma) to a TlI-type structure (space groupCmcm) is investigatedin situ vianeutron powder diffraction (NPD) in the temperature range 298–853 K for the selected composition Sn0.8Ge0.2Se. This transition takes place at 803 K, as shown by differential scanning calorimetry. The analysis from the NPD data shows a non-monotonic behaviour of the anisotropic displacement parameters upon entering the domain of theCmcmstructure. The energies of the atomic vibrations have been quantitatively analysed by fitting the temperature-dependent mean-square displacements to Einstein oscillators. The thermal conductivity of Sn0.8Ge0.2Se is as low as 0.35 W m−1 K−1at 773 K, which mostly represents the lattice thermal contribution.

Crystal data for 1.3-dibromo-5-methylbenzene at 293 K

1985 ◽  
Vol 18 (6) ◽  
pp. 542-542
Author(s):  
A. Belaaraj ◽  
N. B. Chanh ◽  
Y. Haget ◽  
E. Tauler
Keyword(s):  
Phase Transition ◽  
Internal Standard ◽  
Crystal Data ◽  
Orthorhombic Space Group ◽  
Scanning Calorimetry ◽  
Single Crystal Diffraction ◽  
Space Group ◽  
Cell Parameters ◽  
Compound C ◽  
Cell Dimensions

The title compound C7H6Br2 (also called 3,5-dibromotoluene) is orthorhombic, space group P212121 with a = 14.426(2), b = 13.636(2), c = 4.076(1) Å, V = 801.8(3) Å3, Z = 4, Dx = 2.071 Mg m−3. The space group and preliminary cell parameters have been determined by single-crystal diffraction methods (Bragg, Weissenberg and precession patterns). The cell dimensions have been refined by least squares from accurate powder diffractometer data recorded at T = 293(1) K (quartz as internal standard, Cu Kα 1−Kα 2 correction so that λ = 1.54056 Å). The indexed powder data are given. No phase transition is detected between 123 K and the melting point 311.1(2) K (differential scanning calorimetry and Guinier–Lenné analysis). The results show that 1,3-dibromo-5-methylbenzene is isomorphous with 1,3,5-trichlorobenzene and 1,3,5-tribromobenzene. The JCPDS Diffraction File No. For C7H6Br2 is 36-1991.

Structural phase transition in polycrystalline SnSe: a neutron diffraction study in correlation with thermoelectric properties

2016 ◽  
Vol 49 (6) ◽  
pp. 2138-2144 ◽  
Author(s):  
F. Serrano-Sánchez ◽  
N. M. Nemes ◽  
O. J. Dura ◽  
M. T. Fernandez-Diaz ◽  
J. L. Martínez ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase ◽  
Neutron Diffraction Study ◽  
Type Structure ◽  
Scanning Calorimetry ◽  
Space Group ◽  
Temperature Range ◽  
Seebeck Coefficients ◽  
Structure Space ◽  
Arc Melting

SnSe has been recently reported as a promising and highly efficient thermoelectric intermetallic alloy. The present material has been prepared by arc melting, as mechanically robust pellets, consisting of highly oriented polycrystals. The evolution of its orthorhombic GeS-type structure (space groupPnma) and phase transition to TlI-type structure (space groupCmcm) at high temperature has been studiedin situby neutron powder diffraction (NPD) in the temperature range 295–873 K. This transition has been identified by differential scanning calorimetry measurements, yielding sharp peaks at 795 K. In addition, thermal transport properties were measured in a similar temperature range, and large Seebeck coefficients, as high as 1050 µV K−1at 625 K, were found. The analysis from NPD data demonstrates an almost perfect stoichiometry, Sn0.998(8)Se, that does not evolve with temperature, and a progressive decrease of the anharmonicity of the chemical bonds upon entering the domain of theCmcmstructure.

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&ndash;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.

Thermochemistry of the alkali rare-earth double phosphates, A3RE(PO4)2

2004 ◽  
Vol 19 (7) ◽  
pp. 2165-2175 ◽  
Author(s):  
Sergey V. Ushakov ◽  
Alexandra Navrotsky ◽  
J. Matt Farmer ◽  
Lynn A. Boatner
Keyword(s):  
Phase Transition ◽  
Rare Earth ◽  
High Temperature ◽  
Structural Phase ◽  
Formation Enthalpy ◽  
Solution Calorimetry ◽  
Scanning Calorimetry ◽  
Oxide Melt ◽  
Reversible Phase Transition ◽  
High Temperature Oxide

The formation enthalpies for alkali rare-earth compounds of the type K3RE(PO4)2 where RE = Sc, Y, Lu, Er, Ho, Dy, Gd, Nd, or Ce and for A3Lu(PO4)2 compounds with A = K, Rb, or Cs were determined using high-temperature oxide-melt solution calorimetry. Structural phase transitions were observed and characterized using differential scanning calorimetry and high-temperature x-ray diffraction. The formation enthalpy of the K3RE(PO4)2 phases from oxides becomes more exothermic with increasing rare-earth radius for the K3RE(PO4)2 series and with increasing alkali radius for the A3Lu(PO4)2 compounds. The K3RE(PO4)2 phases are stable with respect to anhydrous K3PO4 and REPO4. The monoclinic K3RE(PO4)2 compounds undergo a reversible phase transition to a hexagonal (glaserite-type) structure with a phase transition temperature that increases from −99 to 1197 °C with increasing RE ionic radius going from Lu to Ce.

Reversible phase transition of 2-carboxypyridinium perchlorate–pyridinium-2-carboxylate (1/1)

2015 ◽  
Vol 71 (4) ◽  
pp. 247-251 ◽  
Author(s):  
Bi-Qin Wang ◽  
Hai-Biao Yan ◽  
Zheng-Qing Huang ◽  
Yun-Hua Zhang ◽  
Jing Sun
Keyword(s):  
Phase Transition ◽  
Carboxylic Acid ◽  
Rotation Axis ◽  
Acid Group ◽  
Carboxylic Acid Group ◽  
Tetrahedral Geometry ◽  
Space Group ◽  
Reversible Phase Transition ◽  
Reversible Phase ◽  
Hydrogen Bonded

The title salt, C6H6NO2+·ClO4−·C6H5NO2, was crystallized from an aqueous solution of equimolar quantities of perchloric acid and pyridine-2-carboxylic acid. Differential scanning calorimetry (DSC) measurements show that the compound undergoes a reversible phase transition at about 261.7 K, with a wide heat hysteresis of 21.9 K. The lower-temperature polymorph (denoted LT;T= 223 K) crystallizes in the space groupC2/c, while the higher-temperature polymorph (denoted RT;T= 296 K) crystallizes in the space groupP2/c. The relationship between these two phases can be described as: 2aRT=aLT; 2bRT=bLT;cRT=cLT. The crystal structure contains an infinite zigzag hydrogen-bonded chain network of 2-carboxypyridinium cations. The most distinct difference between the higher (RT) and lower (LT) temperature phases is the change in dihedral angle between the planes of the carboxylic acid group and the pyridinium ring, which leads to the formation of different ten-membered hydrogen-bonded rings. In the RT phase, both the perchlorate anions and the hydrogen-bonded H atom within the carboxylic acid group are disordered. The disordered H atom is located on a twofold rotation axis. In the LT phase, the asymmetric unit is composed of two 2-carboxypyridinium cations, half an ordered perchlorate anion with ideal tetrahedral geometry and a disordered perchlorate anion. The phase transition is attributable to the order–disorder transition of half of the perchlorate anions.

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).

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