High pressure and low temperature X-ray crystallography: the crystal structure of the molecular charge transfer salt α'- (bis(ethylenedithio)-tetrathiafulvalene) 2 AuBr 2

1993 ◽  
Vol 442 (1914) ◽  
pp. 207-219 ◽  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Charge Transfer ◽  
Low Temperature ◽  
Ambient Pressure ◽  
Structural Phase ◽  
X Ray ◽  
X Ray Crystallography ◽  
Molecular Charge ◽  
Transfer Integral

An X-ray diffraction technique is described that allows determination of crystal structure and the variation of lattice parameters of single crystals as a function of hydrostatic pressure up to 14 kbar and of temperature from 300 K to 12 K. As an example of the technique results are presented on the molecular charge transfer salt α'-(BEDT TTF )2 AuBr 2 (BEDT-TTF = bis(ethylenedithio)-tetrathiafulvalene) to elucidate the nature of a structural phase transition which occurs at 250 K at ambient pressure and 7 kbar at 300 K. The transition, of second order, is characterized by the appearance of ½b* superlattice reflections at high pressure or low temperature but without any drastic change in the basic crystal structure. The isobaric thermal expansions and the isothermal compressibilities are anisotropic, being larger along a than along b and c , though of different magnitudes and directional properties, i. e. the effect of applying pressure at ambient temperature is not equivalent to lowering the temperature at ambient pressure. Transfer integral calculations show that marked dimerization along the stacking axis, already present at 300 K, is related to electronic localization.

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.

scholarly journals Lichtabsorption von oxidischen Silber(I)-Verbindungen / Light Absorption of Silver(I)-oxides

1984 ◽  
Vol 39 (6) ◽  
pp. 739-743 ◽  
Author(s):  
Claus Friebel ◽  
Martin Jansen
Keyword(s):  
High Pressure ◽  
Charge Transfer ◽  
Low Temperature ◽  
Absorption Edge ◽  
Diffuse Reflectance ◽  
Static Pressure ◽  
Ambient Pressure ◽  
Partial Structures ◽  
Wide Range ◽  
Charge Transfer Transitions

AbstractDiffuse reflectance spectra of Ag2SO4, Ag3PO4, Ag2CO3, Ag2Ge2O5, AgBO2, Ag3BO3-II, Ag6Si2O7, Ag10Si4O13 and Ag10Ge4O13 in the region ν̄ = 10000-40000 cm-1 and generally at 298 K and ambient pressure were measured. Additional spectra were recorded at 5 K for Ag3BO3 and Ag3PO4, and under application of a static pressure of 80 kbar for Ag10Si4O13. As a common feature all spectra show a steep absorption edge, which is only structured in singular cases. The edges appear in the remarkably wide range from 33100 cm-1 (Ag2SO4) to 13500 cm-1 (Ag10Ge4O13). As the shifts correlate with the dimensions of the cluster-like silver partial structures, the absorptions have been attributed to 4d→5s band-band transitions, an interpretation, which is in agreement with the low temperature and high pressure spectra. However, effects originating from charge-transfer transitions cannot be absolutely excluded.

scholarly journals Structural Phase Diagram of LaO1−xFxBiSSe: Suppression of the Structural Phase Transition by Partial F Substitutions

2020 ◽  
Vol 5 (4) ◽  
pp. 81
Author(s):  
Kazuhisa Hoshi ◽  
Shunsuke Sakuragi ◽  
Takeshi Yajima ◽  
Yosuke Goto ◽  
Akira Miura ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Diagram ◽  
Low Temperature ◽  
Structural Transition ◽  
Structural Phase ◽  
Tetragonal Structure ◽  
Layered Superconductor ◽  
X Ray Diffraction ◽  
X Ray ◽  
Plane Anisotropy

Recently, the anomalous two-fold-symmetric in-plane anisotropy of superconducting states has been observed in a layered superconductor system, LaO1−xFxBiSSe (x = 0.1 and 0.5), with a tetragonal (four-fold symmetric) in-plane structure. To understand the origin of the phenomena observed in LaO1−xFxBiSSe, clarification of the low-temperature structural phase diagram is needed. In this study, we have investigated the low-temperature crystal structure of LaO1−xFxBiSSe (x = 0, 0.01, 0.02, 0.03, and 0.5). From synchrotron X-ray diffraction experiments, a structural transition from tetragonal to monoclinic was observed for x = 0 and 0.01 at 340 and 240 K, respectively. For x = 0.03, a structural transition and broadening of the diffraction peak were not observed down to 100 K. These facts suggest that the structural transition could be suppressed by 3% F substitution in LaO1−xFxBiSSe. Furthermore, the crystal structure for x = 0.5 at 4 K was examined by low-temperature laboratory X-ray diffraction, which confirmed that the tetragonal structure is maintained at 4 K for x = 0.5. Our structural investigation suggests that the two-fold-symmetric in-plane anisotropy of superconducting states observed in LaO1−xFxBiSSe was not originated from structural symmetry lowering in its average structure. To evaluate the possibility of the local structural modification like nanoscale puddles in the average tetragonal structure, further experiments are desired.

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.

scholarly journals Investigation of high-pressure planetary ices by cryo-recovery. I. An apparatus for X-ray powder diffraction from 40 to 315 K, allowing `cold loading' of samples

2018 ◽  
Vol 51 (3) ◽  
pp. 685-691 ◽  
Author(s):  
Ian G. Wood ◽  
A. Dominic Fortes ◽  
David P. Dobson ◽  
Weiwei Wang ◽  
Lucjan Pajdzik ◽  
...  
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Powder Diffraction ◽  
Ambient Pressure ◽  
Temperature Stability ◽  
Extended Period ◽  
Turnaround Time ◽  
Normal Operation ◽  
X Ray ◽  
Sample Chamber

A low-temperature stage for X-ray powder diffraction in Bragg–Brentano reflection geometry is described. The temperature range covered is 40–315 K, with a temperature stability at the sample within ±0.1 K of the set point. The stage operates by means of a Gifford–McMahon (GM) closed-cycle He refrigerator; it requires no refrigerants and so can run for an extended period (in practice at least 5 d) without intervention by the user. The sample is cooled both by thermal conduction through the metal sample holder and by the presence of He exchange gas, at ambient pressure, within the sample chamber; the consumption of He gas is extremely low, being only 0.1 l min−1 during normal operation. A unique feature of this cold stage is that samples may be introduced into (and removed from) the stage at any temperature in the range 80–300 K, and thus materials which are not stable at room temperature, such as high-pressure phases that are recoverable to ambient pressure after quenching to liquid nitrogen temperatures, can be readily examined. A further advantage of this arrangement is that, by enabling the use of pre-cooled samples, it greatly reduces the turnaround time when making measurements on a series of specimens at low temperature.

Synthesis and Structural Study of the Thermochromic Compounds Bis(2-amino-4-oxo-6-methylpyrimidinium) Tetrachlorocuprate(II) and Bis(2-amino-4-chloro-6-methylpyrimidinium) Hexachlorodicuprate(II)

1999 ◽  
Vol 54 (6) ◽  
pp. 718-724 ◽  
Author(s):  
Isabel Díaz ◽  
Vicente Fernández ◽  
Vitaly K. Belsky ◽  
Jose Luis Martínez
Keyword(s):  
Charge Transfer ◽  
Low Temperature ◽  
Magnetic Measurements ◽  
Variable Temperature ◽  
Major Change ◽  
Crystal Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Square Planar ◽  
Intermediate States

The compound bis(2-amino-4-oxo-6-methylpyrimidinium) tetrachlorocuprate(II) 1 contains CuCU42- square-planar anions, and bis(2-amino-4-chloro-6-methylpyrimidinium) hexachlorodicuprate( II) 2 quasi-planar CU2CI62- anions. Both compounds show thermochromic behaviour. This phenomenon has been studied by X-ray crystallography at variable temperature, with the result that no major change is observed in the geometry of the copper atom. Thus it is possible to assume some influence of the hydrogen bonds and o f the different geometries of intermediate states on the color of the compounds due to the modifications provoked in the L→M charge transfer and in the energy o f the metal d-d transitions. Magnetic measurements of the compounds give information on magneto-structural correlations. Compound 1 is ferromagnetic (Tc ≅ 20 K) due to the perpendicular arrangement of the square anions that allows exchange pathways only via Cu-Cl -Cu , H-bonding or cationic n electron interactions. Compound 2 shows a very complicated behavior at low temperature with local antiferromagnetic fluctuations. Crystal data: 1 C10H10N6O2Cl4Cu, triclinic, P1; 393(2) K: α = 11.053(2), b = 11.334(2), c =14.038(3) (Å), α = 95.76(3), β = 101.35(3), γ=90.15(3)(°) ; 293(2) K: a = 11.022(2), b = 11.289(2), c = 14.001(3) (Å), α = 95.86(2), β = 101.34(2), γ=90.09(3)(°) ; 155(2) K: a = 11.008(2), b = 11.231 (2), c = 13.967(3) (A), a = 95.86(2), β = 101.37(2), γ=89.99(2)(°) ; Z = 4. 2 (C5H7N3Cl3Cu)2 , monoclinic, P21/c; 293(2) K: a = 5.998(1), b =18.669(4), c = 9.466(2) (Å), β =100.93(3)(°) ; 150(2) K: a = 5.971(1), b = 18.655(4), c = 9.383(2) (Å), ß =101.64(1)(°);Z=4

Pressure-induced polymorphism in phenol

2002 ◽  
Vol 58 (6) ◽  
pp. 1018-1024 ◽  
Author(s):  
David R. Allan ◽  
Stewart J. Clark ◽  
Alice Dawson ◽  
Pamela A. McGregor ◽  
Simon Parsons
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Ab Initio ◽  
Density Functional ◽  
Ambient Pressure ◽  
Energy Difference ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pressure Melting ◽  
Pressure Phase

The high-pressure crystal structure of phenol (C6H5OH), including the positions of the H atoms, has been determined using a combination of single-crystal X-ray diffraction techniques and ab initio density-functional calculations. It is found that at a pressure of 0.16 GPa, which is just sufficient to cause crystallization of a sample held at a temperature just above its ambient-pressure melting point (313 K), a previously unobserved monoclinic structure with P21 symmetry is formed. The structure is characterized by the formation of hydrogen-bonded molecular chains, and the molecules within each chain adopt a coplanar arrangement so that they are ordered in an alternating 1-1-1 sequence. Although the crystal structure of the ambient-pressure P1121 phase is also characterized by the formation of molecular chains, the molecules adopt an approximate threefold arrangement. A series of ab initio calculations indicates that the rearrangement of the molecules from helical to coplanar results in an energy difference of only 0.162 eV molecule−1 (15.6 kJ mole−1) at 0.16 GPa. The calculations also indicate that there is a slight increase in the dipole moment of the molecules, but, as the high-pressure phase has longer hydrogen-bond distances, it is found that, on average, the hydrogen bonds in the ambient-pressure phase are stronger.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

scholarly journals High-pressure synthesis and crystal structure of the mixed-cation borate Ga4In4B15O33(OH)3

2019 ◽  
Vol 74 (4) ◽  
pp. 357-363
Author(s):  
Daniela Vitzthum ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Mixed Cation ◽  
High Pressure High Temperature ◽  
Pressure Synthesis

AbstractThe mixed cation triel borate Ga4In4B15O33(OH)3 was synthesized in a Walker-type multianvil apparatus at high-pressure/high-temperature conditions of 12.5 GPa and 1300°C. Although the product could not be reproduced in further experiments, its crystal structure could be reliably determined via single-crystal X-ray diffraction data. Ga4In4B15O33(OH)3 crystallizes in the tetragonal space group I41/a (origin choice 2) with the lattice parameters a = 11.382(2), c = 15.244(2) Å, and V = 1974.9(4) Å3. The structure of the quaternary triel borate consists of a complex network of BO4 tetrahedra, edge-sharing InO6 octahedra in dinuclear units, and very dense edge-sharing GaO6 octahedra in tetranuclear units.

Verfeinerung der Kristallstruktur von Tripalladium-di-tetrathiophospliat Pd3(PS4)2 Refinement of the Crystal Structure of Tripalladium-di-tetrathiophosphate Pda3(PS4)2

1983 ◽  
Vol 38 (4) ◽  
pp. 426-427 ◽  
Author(s):  
Arndt Simon ◽  
Karl Peters ◽  
Harry Hahn
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Title Compound ◽  
Type Structure ◽  
Tetrahedral Symmetry ◽  
X Ray ◽  
X Ray Crystallography ◽  
Planar Environment

Abstract The structure of the title compound has been determined by X-ray crystallography. The title compound is synthesized from the elements at 600 °C. Its crystal structure, derived from powder data [3] is refined by single crystal diffractometer data. The structure is trigonal (P3̅ml, α = 684.1(1), c = 724.4(1) pm); Pd2+ cations and PS43- anions form a network with an anti-Claudetite (AS2O3) type structure. The PS4 units are distinctly distorted from ideal tetrahedral symmetry. The Pd atoms have a planar environment of 4 S atoms.

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