High-pressure X-ray diffraction studies of potassium chlorate

2011 ◽  
Vol 45 (1) ◽  
pp. 48-52 ◽  
Author(s):  
Michael Pravica ◽  
Ligang Bai ◽  
Neelanjan Bhattacharya
Keyword(s):  
High Pressure ◽  
Decomposition Rate ◽  
Ambient Pressure ◽  
Rhombohedral Phase ◽  
Potassium Chlorate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Induced Decomposition ◽  
Xrd Patterns ◽  
Pressure Regime

Two static high-pressure X-ray diffraction (XRD) studies of potassium chlorate have been performed at pressures of up to ∼14.3 GPa in a diamond anvil cell at ambient temperature using the 16 ID-B undulator beamline at the Advanced Photon Source for the X-ray source. The first experiment was conducted to ascertain decomposition rates of potassium chlorate as a function of pressure. Below 2 GPa, the sample was observed to decompose rapidly in the presence of the X-ray beam and release oxygen. Above 2 GPa (near the phase I → phase II transition), the decomposition rate dramatically slowed so that good quality XRD patterns could be acquired. This suggests a phase-dependent decomposition rate. In the second study, X-ray diffraction spectra were collected at pressures from 2 to 14.3 GPa by aligning virgin portions of the sample into the focused X-ray beam at each pressure. The results suggest the co-existence of mixed monoclinic (I) and rhombohedral (II) phases of potassium chlorate near 2 GPa. At pressures beyond 4 GPa, the XRD patterns show a very good fit to KClO3in the rhombohedral phase with space groupR3m, in agreement with earlier studies. No further phase transitions were observed with pressure. Decompression of the sample to ambient pressure indicated mixed phases I and II coupled with a small amount of synchrotron X-ray-induced decomposition product. The equation of state within this pressure regime has been determined.

Phase transitions in ReO3studied by high-pressure X-ray diffraction

2000 ◽  
Vol 33 (2) ◽  
pp. 279-284 ◽  
Author(s):  
J.-E. Jørgensen ◽  
J. Staun Olsen ◽  
L. Gerward
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Powder Diffraction ◽  
Ambient Pressure ◽  
Rhombohedral Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Ions ◽  
Pressure Phase ◽  
Related Phase

ReO3has been studied at pressures up to 52 GPa by X-ray powder diffraction. The previously observed cubicIm3¯ high-pressure phase was shown to transform to a monoclinic MnF3-related phase at about 3 GPa. All patterns recorded above 12 GPa could be indexed on rhombohedral cells. The compressibility was observed to decrease abruptly at 38 GPa. It is therefore proposed that the oxygen ions are hexagonally close packed above this pressure, giving rise to two rhombohedral phases labelled I and II. The zero-pressure bulk moduliBoof the observed phases were determined and the rhombohedral phase II was found to have an extremely large value of 617 (10) GPa. It was found that ReO3transforms back to thePm3¯mphase found at ambient pressure.

scholarly journals High-Pressure Structural Behavior and Equation of State of Kagome Staircase Compound, Ni3V2O8

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 910
Author(s):  
Daniel Diaz-Anichtchenko ◽  
Robin Turnbull ◽  
Enrico Bandiello ◽  
Simone Anzellini ◽  
Daniel Errandonea
Keyword(s):  
High Pressure ◽  
Equation Of State ◽  
Density Functional ◽  
Room Temperature ◽  
Ambient Pressure ◽  
Density Functional Theory Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
A Chain

We report on high-pressure synchrotron X-ray diffraction measurements on Ni3V2O8 at room-temperature up to 23 GPa. According to this study, the ambient-pressure orthorhombic structure remains stable up to the highest pressure reached in the experiments. We have also obtained the pressure dependence of the unit-cell parameters, which reveals an anisotropic compression behavior. In addition, a room-temperature pressure–volume third-order Birch–Murnaghan equation of state has been obtained with parameters: V0 = 555.7(2) Å3, K0 = 139(3) GPa, and K0′ = 4.4(3). According to this result, Ni3V2O8 is the least compressible kagome-type vanadate. The changes of the crystal structure under compression have been related to the presence of a chain of edge-sharing NiO6 octahedral units forming kagome staircases interconnected by VO4 rigid tetrahedral units. The reported results are discussed in comparison with high-pressure X-ray diffraction results from isostructural Zn3V2O8 and density-functional theory calculations on several isostructural vanadates.

X-Ray Structural Study of Li3N at High Pressure

1997 ◽  
Vol 499 ◽  
Author(s):  
Allen C. Ho ◽  
Maurice K. Granger ◽  
Arthur L. Ruoff
Keyword(s):  
High Pressure ◽  
Free Energy ◽  
Synchrotron Radiation ◽  
Equation Of State ◽  
Ambient Temperature ◽  
Structural Study ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gibb’S Free Energy

ABSTRACTThe equation of state (EOS) of Li3N has been determined by energy-dispersive x-ray diffraction (EDXD) using synchrotron radiation up to 35 GPa at ambient temperature. Both the hexagonal D6h4(P63/mmc) and the hexagonal D6h1(P6/mmm) phases were present at ambient pressure. The D6h1 -structure completely transforms into the D6h4 -structure at modest pressure. The change in Gibb's free energy as a function of pressure for Li3N was calculated using the experimental EOS.

Crystal Polymorphs and Multiple Crystallization Pathways of Highly Pressurized 1-Ethyl-3-Methylimidazolium Nitrate

2019 ◽  
Vol 72 (2) ◽  
pp. 87 ◽  
Author(s):  
Hiroshi Abe ◽  
Takahiro Takekiyo ◽  
Yukihiro Yoshimura ◽  
Nozomu Hamaya ◽  
Shinichiro Ozawa
Keyword(s):  
Differential Scanning Calorimetry ◽  
High Pressure ◽  
Room Temperature ◽  
Ambient Pressure ◽  
Optical Microscope ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Low Temperature Crystallization ◽  
Temperature Crystallization

Crystal polymorphs and multiple crystallization pathways of a room-temperature ionic liquid (RTIL) were observed only under high pressure (HP). The RTIL was 1-ethyl-3-methylimidazolium nitrate, [C2mim][NO3]. The HP-crystal polymorphs were related to conformations of the C2mim+ cation, and the HP-crystal pathways determined by the presence or absence of the planar′ (P′) conformation of the C2mim+ cation were switched at the bifurcation pressure (PB). Above PB, modulated crystal structures derived from the HP-inherent P′ conformer. Simultaneous X-ray diffraction and differential scanning calorimetry measurements, accompanied by optical microscope observations, confirmed the normal low-temperature crystallization of [C2mim][NO3] under ambient pressure.

scholarly journals The untypical high-pressure Zintl phase SrGe6

2020 ◽  
Vol 75 (1-2) ◽  
pp. 209-216 ◽  
Author(s):  
Ulrich Schwarz ◽  
Rodrigo Castillo ◽  
Julia M. Hübner ◽  
Aron Wosylus ◽  
Yurii Prots ◽  
...  
Keyword(s):  
High Pressure ◽  
Ambient Pressure ◽  
Three Dimensional ◽  
Structure Type ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Quantum Chemical Analysis ◽  
Electronic Density ◽  
X Ray ◽  
High Pressure High Temperature

AbstractThe binary strontium germanide SrGe6 was synthesized at high-pressure high-temperature conditions of approximately 10 GPa and typically 1400 K before quenching to ambient conditions. At ambient pressure, SrGe6 decomposes in a monotropic fashion at T = 680(10) K into SrGe2 and Ge, indicating its metastable character. Single-crystal X-ray diffraction data indicate that the compound SrGe6 adopts a new monoclinic structure type comprising a unique three-dimensional framework of germanium atoms with unusual cages hosting the strontium cations. Quantum chemical analysis of the chemical bonding shows that the framework consists of three- and four- bonded germanium atoms yielding the precise electron count Sr[(4bGe0]4[(3b)Ge−]2 in accordance with the 8 − N rule and the Zintl concept. Conflicting with that, a pseudo-gap in the electronic density of states appears clearly below the Fermi level, and elaborate bonding analysis reveals additional Sr–Ge interactions in the concave coordination polyhedron of the strontium atoms.

scholarly journals High-Pressure Syntheses, Crystal Structures, And Thermal Behaviour Of β-Re(Bo2)3 (Re = Nd, Sm, Gd)

2007 ◽  
Vol 62 (6) ◽  
pp. 765-770 ◽  
Author(s):  
Holger Emme ◽  
Gunter Heymann ◽  
Almut Haberer ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Single Crystal ◽  
Crystal Structures ◽  
Thermal Behaviour ◽  
Diffraction Data ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Conditions

The compounds β -RE(BO2)3 [RE = Nd (neodymium meta-borate), Sm (samarium meta-borate) and Gd (gadolinium meta-borate)] were synthesized under high-pressure and high-temperature conditions in a Walker-type multianvil apparatus at 3.5 GPa (Nd), 7.5 GPa (Sm, Gd) and 1050 °C. The crystal structures were determined by single crystal X-ray diffraction data collected at r. t. (Sm, Gd) and at−73°C (Nd), respectively. The structures are isotypic with the already known ambient-pressure phases β -RE(BO2)3 (RE = (Tb, Dy) and the high-pressure phases β -RE(BO2)3 (RE = Ho-Lu)

scholarly journals Thermodynamic and kinetic isotope effects on the order–disorder transition of ice XIV to ice XII

2018 ◽  
Vol 20 (33) ◽  
pp. 21607-21616 ◽  
Author(s):  
Violeta Fuentes-Landete ◽  
Karsten W. Köster ◽  
Roland Böhmer ◽  
Thomas Loerting
Keyword(s):  
High Pressure ◽  
Dielectric Spectroscopy ◽  
Ambient Pressure ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
X Ray Diffraction ◽  
Disorder Transition ◽  
X Ray ◽  
Kinetic Isotope

Isotope effects accompanying the order–disorder transition of ice XIV to ice XII are studied using calorimetry, X-ray diffraction, and dielectric spectroscopy, both at high-pressure and ambient pressure conditions.

scholarly journals Stoichiometric evolutions of PH3 under high pressure: implication for high-Tc superconducting hydrides

2019 ◽  
Vol 6 (3) ◽  
pp. 524-531 ◽  
Author(s):  
Ye Yuan ◽  
Yinwei Li ◽  
Guoyong Fang ◽  
Guangtao Liu ◽  
Cuiying Pei ◽  
...  
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
Recent Observation ◽  
Theoretical Calculations ◽  
Ambient Pressure ◽  
Superconducting Transition ◽  
X Ray Diffraction ◽  
Elemental Phosphorus ◽  
High Tc ◽  
X Ray

Abstract The superconductivity of hydrides under high pressure has attracted a great deal of attention since the recent observation of the superconducting transition at 203 K in strongly compressed H2S. It has been realized that the stoichiometry of hydrides might change under high pressure, which is crucial in understanding the superconducting mechanism. In this study, PH3 was studied to understand its superconducting transition and stoichiometry under high pressure using Raman, IR and X-ray diffraction measurements, as well as theoretical calculations. PH3 is stable below 11.7 GPa and then it starts to dehydrogenate through two dimerization processes at room temperature and pressures up to 25 GPa. Two resulting phosphorus hydrides, P2H4 and P4H6, were verified experimentally and can be recovered to ambient pressure. Under further compression above 35 GPa, the P4H6 directly decomposed into elemental phosphorus. Low temperature can greatly hinder polymerization/decomposition under high pressure and retains P4H6 up to at least 205 GPa. The superconductivity transition temperature of P4H6 is predicted to be 67 K at 200 GPa, which agrees with the reported result, suggesting that it might be responsible for superconductivity at higher pressures. Our results clearly show that P2H4 and P4H6 are the only stable P–H compounds between PH3 and elemental phosphorus, which is helpful for shedding light on the superconducting mechanism.

scholarly journals Microstructure and Nanohardness of Ti-48Al-2Cr Alloy Solidified under High Pressure

2020 ◽  
Vol 10 (15) ◽  
pp. 5394
Author(s):  
Duo Dong ◽  
Li Liu ◽  
Dongdong Zhu ◽  
Yang Liu ◽  
Ye Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Lamellar Structure ◽  
Ambient Pressure ◽  
Testing Machine ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microstructure Observation ◽  
Transmission Electron ◽  
Holding Temperature

In this work, the Ti-48Al-2Cr alloy, solidified under different pressures and temperatures, was investigated in detail. The effect of high pressure on the microstructure and nanohardness of the Ti-48Al-2Cr alloy was investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and a nanoindenter XP testing machine. The results showed that the B2 phase disappeared after high-pressure solidification. Compared with ambient pressure solidification, high pressure led to the increase of (α2 + γ) lamellar structure and the decrease of γ phase. The nanohardness of the lamellar structure was discussed based on the microstructure observation. When solidified at 5 GPa/1873 K, the hardness rose to 5.54 GPa, an increase of 60.5% compared with that solidified at ambient pressure. However, the increased holding temperature of 1973 K made the dislocation density in the lamellar structures greatly decrease, and reduced the structure’s hardness to 4.48 GPa.

Structure-Reactivity Relationships of Anatase and Rutile TiO2 Nanocrystals Measured by In Situ Vibrational Spectroscopy

2010 ◽  
Vol 162 ◽  
pp. 203-219 ◽  
Author(s):  
Lars Österlund
Keyword(s):  
Formic Acid ◽  
Vibrational Spectroscopy ◽  
Decomposition Rate ◽  
Comprehensive Analysis ◽  
X Ray Diffraction ◽  
Tio2 Nanocrystals ◽  
X Ray ◽  
Induced Decomposition ◽  
Adsorbate Structure

A comprehensive analysis of structural-reactivity relations on TiO2 nanocrystals is presented. Using an interplay between TEM, X-ray diffraction and vibrational spectroscopy of well-defined anatase and rutile TiO2 nanocrystals correlations between the adsorbate structure of formic acid and the corresponding photo-induced decomposition rate are described. It is demonstrated that the detailed bonding configuration determines the decomposition rate. Generalizations and implications of the findings are discussed.

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