Low-temperature structure of V6O13

2003 ◽  
Vol 59 (6) ◽  
pp. 747-752 ◽  
Author(s):  
Jonas Höwing ◽  
Torbjörn Gustafsson ◽  
John O. Thomas
Keyword(s):  
Low Temperature ◽  
Mirror Plane ◽  
Temperature Phase ◽  
Temperature Structure ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Acta Cryst ◽  
Lithium Polymer Batteries ◽  
Space Group ◽  
Dsc Measurements

The structure of the transition metal oxide V6O13, a potential cathode material in lithium-polymer batteries, has been studied at 95 K using single-crystal X-ray diffraction (XRD). A phase transition has been determined by differential scanning calorimetry (DSC) measurements to occur at 153 K, with a heat of transition of −1.98 kJ mol−1. In this low-temperature phase, the V and O atoms move by up to 0.21 Å out of the mirror plane they occupy in the room-temperature structure. It is concluded that the earlier reported space group P21/a [Kawada et al. (1978). Acta Cryst. B34, 1037–1039] is incorrect and that a more appropriate choice of space group is Pc.

The structures and phase transitions in 4-aminopyridinium tetraaquabis(sulfato)iron(III), (C5H7N2)[FeIII(H2O)4(SO4)2]

2019 ◽  
Vol 75 (6) ◽  
pp. 1144-1151
Author(s):  
Tamara J. Bednarchuk ◽  
Wolfgang Hornfeck ◽  
Vasyl Kinzhybalo ◽  
Zhengyang Zhou ◽  
Michal Dušek ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Single Crystal ◽  
Room Temperature ◽  
Variable Temperature ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Hybrid Compound ◽  
Space Group ◽  
X Ray

The organic–inorganic hybrid compound 4-aminopyridinium tetraaquabis(sulfato)iron(III), (C5H7N2)[FeIII(H2O)4(SO4)2] (4apFeS), was obtained by slow evaporation of the solvent at room temperature and characterized by single-crystal X-ray diffraction in the temperature range from 290 to 80 K. Differential scanning calorimetry revealed that the title compound undergoes a sequence of three reversible phase transitions, which has been verified by variable-temperature X-ray diffraction analysis during cooling–heating cycles over the temperature ranges 290–100–290 K. In the room-temperature phase (I), space group C2/c, oxygen atoms from the closest Fe-atom environment (octahedral) were disordered over two equivalent positions around a twofold axis. Two intermediate phases (II), (III) were solved and refined as incommensurately modulated structures, employing the superspace formalism applied to single-crystal X-ray diffraction data. Both structures can be described in the (3+1)-dimensional monoclinic X2/c(α,0,γ)0s superspace group (where X is ½, ½, 0, ½) with modulation wavevectors q = (0.2943, 0, 0.5640) and q = (0.3366, 0, 0.5544) for phases (II) and (III), respectively. The completely ordered low-temperature phase (IV) was refined with the twinning model in the triclinic P{\overline 1} space group, revealing the existence of two domains. The dynamics of the disordered anionic substructure in the 4apFeS crystal seems to play an essential role in the phase transition mechanisms. The discrete organic moieties were found to be fully ordered even at room temperature.

High- and low-temperature phases in isostructural 4-chloro-3-nitroaniline and 4-iodo-3-nitroaniline

2014 ◽  
Vol 70 (12) ◽  
pp. 1153-1160 ◽  
Author(s):  
Jan Fábry ◽  
Michal Dušek ◽  
Přemysl Vaněk ◽  
Iegor Rafalovskyi ◽  
Jiří Hlinka ◽  
...  
Keyword(s):  
Phase Transitions ◽  
High Temperature ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Primary Amine ◽  
Zigzag Chain ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
Acta Cryst ◽  
Graph Set

The structures of 4-chloro-3-nitroaniline, C6H5ClN2O2, (I), and 4-iodo-3-nitroaniline, C6H5IN2O2, (II), are isomorphs and both undergo continuous (second order) phase transitions at 237 and 200 K, respectively. The structures, as well as their phase transitions, have been studied by single-crystal X-ray diffraction, Raman spectroscopy and difference scanning calorimetry experiments. Both high-temperature phases (293 K) show disorder of the nitro substituents, which are inclined towards the benzene-ring planes at two different orientations. In the low-temperature phases (120 K), both inclination angles are well maintained, while the disorder is removed. Concomitantly, thebaxis doubles with respect to the room-temperature cell. Each of the low-temperature phases of (I) and (II) contains two pairs of independent molecules, where the molecules in each pair are related by noncrystallographic inversion centres. The molecules within each pair have the same absolute value of the inclination angle. The Flack parameter of the low-temperature phases is very close to 0.5, indicating inversion twinning. This can be envisaged as stacking faults in the low-temperature phases. It seems that competition between the primary amine–nitro N—H...O hydrogen bonds which form three-centred hydrogen bonds is the reason for the disorder of the nitro groups, as well as for the phase transition in both (I) and (II). The backbones of the structures are formed by N—H...N hydrogen bonding of moderate strength which results in the graph-set motifC(3). This graph-set motif forms a zigzag chain parallel to the monoclinicbaxis and is maintained in both the high- and the low-temperature structures. The primary amine groups are pyramidal, with similar geometric values in all four determinations. The high-temperature phase of (II) has been described previously [Gardenet al.(2004).Acta Cryst.C60, o328–o330].

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

Towards a more reliable symmetry determination from powder diffraction: a redetermination of the low-temperature structure of 4-methylpyridine-N-oxide

2009 ◽  
Vol 65 (6) ◽  
pp. 784-786 ◽  
Author(s):  
Lukáš Palatinus ◽  
Françoise Damay
Keyword(s):  
Low Temperature ◽  
Powder Diffraction ◽  
Tunneling Spectroscopy ◽  
Temperature Structure ◽  
Determination Method ◽  
Neutron Data ◽  
Acta Cryst ◽  
Space Group ◽  
X Ray ◽  
New Space

The low-temperature structure of 4-methylpyridine-N-oxide was previously determined in symmetry P41 [Damay et al. (2006), Acta Cryst. B62, 627–633]. Using a recently published symmetry-determination method it was found that the true symmetry of the structure is P41212. The structure was refined in the new space group using X-ray and neutron data. The previously published structure is close to the newly refined structure, but the new structure is in agreement with the results of rotational tunneling spectroscopy, and, in contrast to the structure in symmetry P41, does not require a twofold degeneracy of the tunneling bands.

A low temperature phase of (NH4)2TeBr6

1969 ◽  
Vol 47 (22) ◽  
pp. 4288-4289 ◽  
Author(s):  
A. K. Das ◽  
I. D. Brown
Keyword(s):  
Low Temperature ◽  
Tetragonal Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Low Temperature Phase

X-Ray diffraction has shown the existence of a low temperature tetragonal phase of (NH4)2TeBr6 having space group P4/mnc(D4h6) with a = 7.501, c = 10.765 Å.

Order and disorder in acenaphthylene

1973 ◽  
Vol 334 (1596) ◽  
pp. 19-48 ◽  
Keyword(s):  
Low Temperature ◽  
Room Temperature ◽  
Temperature Structure ◽  
Intermediate Form ◽  
X Ray Diffraction ◽  
Space Group ◽  
Order And Disorder ◽  
Temperature Form ◽  
Diffraction Effects

Acenaphthylene, C 12 H 8 , occurs in space group Pbam (or Pba2) at room temperatures (23 °C) with a = 7.705 (5), b = 7.865 (5), c = 14.071 (5) Å and Z = 4, and is disordered. At about 130 K it undergoes a reversible transition to space group P2 1 nm with a = 7.588 (13), b = 7.549 (10), c = 27.822 (2) Å and Z = 8 (85 K) with an ordered structure. A general study of the system has revealed that the structure of both forms consists of layers of closely packed molecules stacked in the c direction. The room temperature structure has a two-layer repeat and the low temperature form a four-layer repeat. Observation of diffuse X-ray diffraction effects at temperatures close to the transition indicates that an intermediate form having a six-layer repeat is formed. A preliminary structure determination of the low-temperature form reveals that the four layers though having a similar packing scheme differ in the orientation of the constituent molecules relative to c . It is proposed that the almost circular shape of the molecules allows each layer to change its identity under thermal agitation by a rotation of its constituent molecules in their own planes. The transition can be explained in terms of changes of the correlations between neighbouring layers. A simple model based on short-range order parameters is described, which explains the occurrence of the six-layer intermediate and the observed sequence of diffuse diffraction phenomena. The nature of the structure of the disordered room temperature form, which is predicted by this model, is confirmed as far as possible with the data available which are limited because of the dearth of high-angle diffraction maxima.

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.

Redetermination of the structure and dielectric properties of bis(thiourea) pyridinium iodide – a new ferroelectric inclusion compound

2008 ◽  
Vol 64 (5) ◽  
pp. 567-572 ◽  
Author(s):  
H. Małuszyńska ◽  
P. Czarnecki ◽  
Z. Fojud ◽  
J. Wąsicki
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Intermediate Phase ◽  
Phase Iii ◽  
Mirror Plane ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Ferroelectric Crystal ◽  
Space Groups

The crystal structure of bis(thiourea) pyridinium iodide (T2PyI) was previously determined at 295 and 110 K [Prout, Heyes, Dobson, McDaid, Maris, Mueller & Seaman (2000). Chem. Mater. 12, 3561–3569] and the two phases were described in the space groups Cmcm and P21 cn, respectively. Because differential scanning calorimetry revealed two phase transitions, at 161 and 141 K, a redetermination of the structure of T2pyI at 295, 155 and 110 K has been undertaken, and the following sequence of space groups obtained: Cmcm (I) → C2cm (II) → P21 cn (III). The high- (I) and low-temperature (III) phases confirmed the results reported in the previous study. In the new intermediate phase II, the mirror plane perpendicular to the x axis vanishes and the crystal structure loses the centre of symmetry. In phases I and II the pyridinium cations are strongly dynamically disordered, while in the low-temperature phase III the cations are well ordered. In all three phases the thiourea–iodine hydrogen-bonded sublattice is very well ordered. Dielectric measurements show that the intermediate and low-temperature phases are ferroelectric and that 161 K is the Curie point of a new ferroelectric crystal.

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 [(1,2,5,6-η)-Cycloocta-1,5-diene]bis(thiocyanato-κS)platinum(II)

IUCrData ◽  
2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Kwang Ha
Keyword(s):  
Room Temperature ◽  
Title Complex ◽  
Mirror Plane ◽  
Temperature Structure ◽  
Orthorhombic Space Group ◽  
Acta Cryst ◽  
Higher Symmetry ◽  
Space Group ◽  
Square Planar ◽  
Plane Passing

In the title complex, [Pt(SCN)2(C8H12)], the PtII ion lies in a square-planar coordination geometry defined by the mid-points of the two π-coordinated double bonds of cycloocta-1,5-diene and two S-bound SCN− anions. The complex is disposed about a mirror plane passing through the Pt atom and the SCN− ligands, and bisecting the cycloocta-1,5-diene molecule. The room-temperature crystal structure of the title complex was previously reported in the orthorhombic space group Pna21 [Musitu & Garcia-Blanco (1984). Acta Cryst. A40, C101]. The low-temperature structure presented herein represents a different (higher symmetry) orthorhombic space group Pnma whereby the PtII atom lies on a mirror plane, lacking in the earlier study.

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