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.

The first proof of protonated anion tetrahedra in the tsumcorite-type compounds

2004 ◽  
Vol 68 (5) ◽  
pp. 757-767 ◽  
Author(s):  
T. Mihajlović ◽  
H. Effenberger
Keyword(s):  
Crystal Structure ◽  
Hydrothermal Synthesis ◽  
Single Crystal ◽  
Diffraction Data ◽  
Title Compound ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
Synthetic Compounds ◽  
X Ray

AbstractHydrothermal synthesis produced the new compound SrCo2(AsO4)(AsO3OH)(OH)(H2O). The compound belongs to the tsumcorite group (natural and synthetic compounds with the general formula M(1)M(2)2(XO4)2(H2O,OH)2; M(1)1+,2+,3+ = Na, K, Rb, Ag, NH4, Ca, Pb, Bi, Tl; M(2)2+,3+ = Al, Mn3+, Fe3+, Co, Ni, Cu, Zn; and X5+,6+ = P, As, V, S, Se, Mo). It represents (1) the first Sr member, (2) the until now unknown [7]-coordination for the M(1) position, (3) the first proof of (partially) protonated arsenate groups in this group of compounds, and (4) a new structure variant.The crystal structure of the title compound was determined using single-crystal X-ray diffraction data. The compound is monoclinic, space group P21/a, with a = 9.139(2), b = 12.829(3), c = 7.522(2) Å, β = 114.33(3)°, V = 803.6(3) Å3, Z = 4 [wR2 = 0.065 for 3530 unique reflections]. The hydrogen atoms were located experimentally.

Structural stability of WS2 under high pressure

2014 ◽  
Vol 28 (25) ◽  
pp. 1450168 ◽  
Author(s):  
Nirup Bandaru ◽  
Ravhi S. Kumar ◽  
Jason Baker ◽  
Oliver Tschauner ◽  
Thomas Hartmann ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Structural Changes ◽  
High Pressures ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diamond Anvil ◽  
Heating Up

Structural behavior of bulk WS 2 under high pressure was investigated using synchrotron X-ray diffraction and diamond anvil cell up to 52 GPa along with high temperature X-ray diffraction and high pressure Raman spectroscopy analysis. The high pressure results obtained from X-ray diffraction and Raman analysis did not show any pressure induced structural phase transformations up to 52 GPa. The high temperature results show that the WS 2 crystal structure is stable upon heating up to 600°C. Furthermore, the powder X-ray diffraction obtained on shock subjected WS 2 to high pressures up to 10 GPa also did not reveal any structural changes. Our results suggest that even though WS 2 is less compressible than the isostructural MoS 2, its crystal structure is stable under static and dynamic compressions up to the experimental limit.

Synthesis, crystal structure, and X-ray diffraction data of lithium m-phenylenediamine sulfate Li2(C6H10N2)(SO4)2

2021 ◽  
pp. 1-5
Author(s):  
Junyan Zhou ◽  
Congcong Chai ◽  
Munan Hao ◽  
Xin Zhong
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Structural Phase ◽  
Measured Temperature ◽  
X Ray Diffraction ◽  
Monoclinic System ◽  
X Ray ◽  
Cell Parameters ◽  
Anisotropic Expansion ◽  
Diffraction Patterns

A new organic–inorganic hybrid lithium m-phenylenediamine sulfate (LPS), Li2(C6H10N2)(SO4)2, was synthesized under aqueous solution conditions. The X-ray powder diffraction study determined that the title compound crystallized in a monoclinic system at 300 K, with unit-cell parameters a = 7.8689(6) Å, b = 6.6353(5) Å, c = 11.8322(10) Å, β = 109.385(3) °, V = 582.77(8) Å3. Indexing of the diffraction patterns collected from 100 to 600 K reveals that LPS has no structural phase transition within the measured temperature range, and the volume expansion coefficient is approximately 2.79 × 10−5 K−1. The crystal structure was solved based on the single-crystal diffraction data with space group P21/m. Lithium and SO42− are found to form quasi-two-dimensional anti-fluorite [LiSO4] layers stacking along the c-axis, with m-phenylenediamine molecules inserted in the anti-fluorite layers and forming hydrogen bonds to the SO42−. This explains a moderate anisotropic expansion in LPS.

The two-step phase transition of titanite, CaTiSiO5: a synchrotron radiation study

1997 ◽  
Vol 212 (1) ◽  
Author(s):  
S. Kek ◽  
M. Aroyo ◽  
U. Bismayer ◽  
C. Schmidt ◽  
K. Eichhorn ◽  
...  
Keyword(s):  
Phase Transition ◽  
Synchrotron Radiation ◽  
Diffraction Data ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Radiation Study

AbstractIn this study it is shown that the antiferrodistortive phase transition in titanite, CaTiSiOIn order to study the stepwise structural changes synchrotron radiation was used to collect X-ray diffraction data at 100 K, 295 K and 530 K on the 4-circle diffractometer at HASYLAB using a wavelength of 0.560(1) Å. A total of 2292 reflections were recorded at 100 K, 1540 at 295 K and 1442 at 530 K and reduced to 705 (100 K), 707 (295 K) and 358 (530 K) unique observations respectively (sin

scholarly journals Intermolecular interactions and charge transfer in the 2:1 tetrathiafulvalene bromanil complex, (TTF)2-BA

2011 ◽  
Vol 67 (3) ◽  
pp. 244-249 ◽  
Author(s):  
Pilar García-Orduña ◽  
Slimane Dahaoui ◽  
Claude Lecomte
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Charge Transfer ◽  
Room Temperature ◽  
Charge Transfer Complex ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Donor And Acceptor ◽  
A Charge

The crystal structure of the 2:1 charge-transfer complex of tetrathiafulvalene [2,2′-bis(1,3-dithiolylidene)] and bromanil (tetrabromo-1,4-benzoquinone) [(TTF)2-BA, (C6H4S4)2–C6Br4O2] has been determined by X-ray diffraction at room temperature, 100 and 25 K. No structural phase transition occurs in the temperature range studied. The crystal is made of TTF–BA–TTF sandwich trimers. A charge-transfer estimation between donor and acceptor (0.2 e) molecules is proposed in comparison to the molecular geometries of TTF–BA and TTF and BA isolated molecules. Displacement parameters of the molecules have been modeled with the TLS formalism.

Powder X-ray diffraction of levothyroxine sodium pentahydrate, C15H10I4NNaO4(H2O)5

2015 ◽  
Vol 30 (4) ◽  
pp. 370-371
Author(s):  
J.A. Kaduk ◽  
K. Zhong ◽  
T.N. Blanton ◽  
S. Gates ◽  
T.G. Fawcett
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Room Temperature ◽  
Levothyroxine Sodium ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Synchrotron Powder Diffraction

The room-temperature crystal structure of levothyroxine sodium pentahydrate has been refined using synchrotron powder diffraction data. The compound crystallizes in space group P1 (#1) with a = 8.2489(4), b = 9.4868(5), c = 15.8298(6) Å, α = 84.1387(4), β = 83.1560(3), γ = 85.0482(3) deg, V = 1220.071(9) Å3, and Z = 2. Hydrogen atoms (missing from the previously-reported structure) were included.

Revision of the crystal structure of “‘bis glycine’ squarate” [Tyagi et al., RSC Adv., 2016, 6, 24565]

2018 ◽  
Author(s):  
Rüdiger W. Seidel
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Correct Placement

The crystal structure of “‘bis glycine’ squarate”, recently published in RSC Advances [Tyagi et al., RSC Adv. 2016, 6, 24565], is revised. Re-refinement of the structure against<br>the original X-ray diffraction data after correct placement of the donor hydrogen atoms proves that the compound is the previously reported diglycinium squarate [Aniola et al.,<br>New J. Chem. 2014, 38, 3556].

Revision of the crystal structure of “‘bis glycine’ squarate” [Tyagi et al., RSC Adv., 2016, 6, 24565]

2018 ◽  
Author(s):  
Rüdiger W. Seidel
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Correct Placement

The crystal structure of “‘bis glycine’ squarate”, recently published in RSC Advances [Tyagi et al., RSC Adv. 2016, 6, 24565], is revised. Re-refinement of the structure against<br>the original X-ray diffraction data after correct placement of the donor hydrogen atoms proves that the compound is the previously reported diglycinium squarate [Aniola et al.,<br>New J. Chem. 2014, 38, 3556].

scholarly journals High-pressure structural study of L-α-glutamine and the use of Hirshfeld surfaces and graph-set notation to investigate the hydrogen bonding present in the structure up to 4.9 GPa

2008 ◽  
Vol 64 (4) ◽  
pp. 466-475 ◽  
Author(s):  
P. Lozano-Casal ◽  
D. R. Allan ◽  
S. Parsons
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
High Pressure ◽  
Room Temperature ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Layer Arrangement ◽  
Hirshfeld Surfaces ◽  
Graph Set

The crystal structure of L-α-glutamine has been elucidated at room temperature at pressures between 0 and 4.9 GPa by using single-crystal high-pressure X-ray diffraction techniques. The structure is primarily stabilized by five N—H...O intermolecular interactions, which link molecules in a herringbone-like layer arrangement, giving rise to voids within the solid. The application of pressure on the structure results in a reduction in the size of the voids, as a consequence of the shortening of the N—H...O hydrogen bonds, which compress to minimum N...O distances of around 2.6 Å, without driving the crystal structure to a phase transition. The decrease in the hydrogen-bond distances is due to the necessary stabilization of the structure, which arises from molecules modifying their positions to optimize electrostatic contacts and minimize the occupied space. Hirshfeld surfaces and fingerprint plots have been used to rapidly assess the structural changes that occur on application of pressure.

scholarly journals Understanding complex phase transition mechanism by crystal structure analysis

2014 ◽  
Vol 70 (a1) ◽  
pp. C1704-C1704
Author(s):  
Kristīne Krūkle-Bērziņa ◽  
Andris Actiņš
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Single Crystal ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Crystal Structure Analysis ◽  
Stable Form ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transition Mechanism

Xylazine hydrochloride (2-(2,6-xylidino)-5,6-dihydro-4H-1,3-thiazine hydrochloride) is an adrenergic α-agonist used as a sedative, analgesic, and muscle relaxant in veterinary medicine. It has four polymorphous forms (A, Z, M and X), monohydrate (H), hemihydrate and solvates with dichloromethane and 2-propanol. It has been reported that the polymorph X is thermodynamically the least stable of these polymorphs, while the A is the most stable form at temperatures above 500C. The X forms only in H dehydration process, and at elevated temperature X transforms to polymorph A [1]. The crystal structures of the polymorphs A and X as well as hydrate H have been reported. Crystal structure of A and X have been determined from the powder X-ray diffraction data (PXRD), whereas that of hydrate have been determined from single crystal X-ray diffraction data [2-3]. In this study structure of A have been determined from single crystal data and compared to that determined by PXRD data. Crystal structures of A, X and H have been compared and analysed. Molecule conformation in crystal structure of all three forms is the same and molecular packing is similar. However, that in monohydrate H and polymorph X is basically the same and the only difference is the inclusion of the water molecules next to the chlorine anions, whereas relative xylazine moiety orientation and arrangement of the chlorine anions is different in the structure of polymorph A. The structural similarity or differences between all three forms noted above were also approved by the 2D-fingerprint plots of the Hirshfeld surfaces. Analysis of all three form crystal structures allowed to better understand complex solid-state phase transition from xylazine hydrochloride polymorph X to polymorph A during and after the dehydration of it monohydrate H.

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