First high-pressure XAFS results at the bending-magnet-based energy-dispersive XAFS beamline BL-8 at the Indus-2 synchrotron facility

2020 ◽  
Vol 27 (4) ◽  
pp. 988-998
Author(s):  
Debdutta Lahiri ◽  
Ashutosh Dwivedi ◽  
R. Vasanthi ◽  
S. N. Jha ◽  
Nandini Garg
Keyword(s):  
High Pressure ◽  
Spot Size ◽  
Energy Dispersive ◽  
Photon Statistics ◽  
Ambient Conditions ◽  
Slit Position ◽  
Synchrotron Facility ◽  
Sample Position ◽  
Diamond Anvil ◽  
Selection Of

The static focusing optics of the existing energy-dispersive XAFS beamline BL-8 have been advantageously exploited to initiate diamond anvil cell based high-pressure XANES experiments at the Indus-2 synchrotron facility, India. In the framework of the limited photon statistics with the 2.5 GeV bending-magnet source, limited focusing optics and 4 mm-thick diamond windows of the sample cell, a (non-trivial) beamline alignment method for maximizing photon statistics at the sample position has been designed. Key strategies include the selection of a high X-ray energy edge, the truncation of the smallest achievable focal spot size to target size with a slit and optimization of the horizontal slit position for transmission of the desired energy band. A motor-scanning program for precise sample centering has been developed. These details are presented with rationalization for every step. With these strategies, Nb K-edge XANES spectra for Nb2O5 under high pressure (0–16.9 GPa) have been generated, reproducing the reported spectra for Nb2O5 under ambient conditions and high pressure. These first HPXANES results are reported in this paper. The scope of extending good data quality to the EXAFS range in the future is addressed. This work should inspire and guide future high-pressure XAFS experiments with comparable infrastructure.

scholarly journals Compressibility of synthetic Mg-Al tourmalines to 60 GPa

2019 ◽  
Vol 104 (7) ◽  
pp. 1005-1015 ◽  
Author(s):  
Eleanor J. Berryman ◽  
Dongzhou Zhang ◽  
Bernd Wunder ◽  
Thomas S. Duffy
Keyword(s):  
High Pressure ◽  
Ring Structure ◽  
Primary Control ◽  
Ambient Conditions ◽  
Cell Parameters ◽  
Al Content ◽  
Tour Maline ◽  
Diamond Anvil ◽  
Diffraction Patterns ◽  
Volume Equation

Abstract High-pressure single-crystal X-ray diffraction patterns on five synthetic Mg-Al tourmalines with near end-member compositions [dravite NaMg3Al6Si6O18(BO3)3(OH)3OH, K-dravite KMg3Al6Si6O18(BO3)3(OH)3OH, magnesio-foitite □(Mg2Al)Al6Si6O18(BO3)3(OH)3OH, oxy-uvite CaMg3Al6Si6O18(BO3)3(OH)3O, and olenite NaAl3Al6Si6O18(BO3)3O3OH, where □ represents an X-site vacancy] were collected to 60 GPa at 300 K using a diamond-anvil cell and synchrotron radiation. No phase transitions were observed for any of the investigated compositions. The refined unit-cell parameters were used to constrain third-order Birch-Murnaghan pressure-volume equation of states with the following isothermal bulk moduli (K0 in GPa) and corresponding pressure derivatives (K0′ = ∂K0/∂P)T: dravite K0 = 97(6), K0′ = 5.0(5); K-dravite K0 = 109(4), K0′ = 4.3(2); oxy-uvite K0 = 110(2), K0′ = 4.1(1); magnesio-foitite K0 = 116(2), K0′ = 3.5(1); olenite K0 = 116(6), K0′ = 4.7(4). Each tour-maline exhibits highly anisotropic behavior under compression, with the c axis 2.8–3.6 times more compressible than the a axis at ambient conditions. This anisotropy decreases strongly with increasing pressure and the c axis is onlŷ14% more compressible than the a axis near 60 GPa. The octahedral Y- and Z-sites' composition exerts a primary control on tourmaline's compressibility, whereby Al content is correlated with a decrease in the c-axis compressibility and a corresponding increase in K0 and K0′. Contrary to expectations, the identity of the X-site-occupying ion (Na, K, or Ca) does not have a demonstrable effect on tourmaline's compression curve. The presence of a fully vacant X site in magnesio-foitite results in a decrease of K0′ relative to the alkali and Ca tourmalines. The decrease in K0′ for magnesio-foitite is accounted for by an increase in compressibility along the a axis at high pressure, reflecting increased compression of tourmaline's ring structure in the presence of a vacant X site. This study highlights the utility of synthetic crystals in untangling the effect of composition on tourmaline's compression behavior.

Energy Dispersive Diffraction in a Diamond Anvil High Pressure Cell Using Synchrotron and Conventional X-Radiation

1983 ◽  
Vol 27 ◽  
pp. 331-337
Author(s):  
David R. Black ◽  
Carmen S. Menoni ◽  
Ian L. Spain
Keyword(s):  
High Pressure ◽  
Energy Dispersive ◽  
X Rays ◽  
High Pressure Cell ◽  
X Ray ◽  
Detection Techniques ◽  
Wide Range ◽  
Diamond Anvil ◽  
Experimental Geometry ◽  
Energy Dispersive Diffraction

A wide range of structural studies have been carried out in high pressure diamond anvil cells using x-rays. The most common experimental geometry is shown in Fig. 1a. The incident x-ray beam passes axially through the first diamond and enters the sample, typically 100-300 μm in diameter and 20-100 μm thick; the diffracted x-rays exit via the second diamond. Energy-dispersive detection techniques (EDXRD) have been used. However the intensity of diffracted radiation from the sample is weak, so that typical exposure times with a conventional, fixed anode, x-ray source are typically one to several days.Accordingly, higher intensity radiation from synchrotron sources has been used for these experiments.

Diffractometric crystal centering

1999 ◽  
Vol 32 (3) ◽  
pp. 510-515 ◽  
Author(s):  
Przemyslaw Dera ◽  
Andrzej Katrusiak
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Crystal Lattice ◽  
Radiation Source ◽  
Prior Information ◽  
High Accuracy ◽  
Sample Position ◽  
Diamond Anvil ◽  
Significant Factors

A general formalism for centering a single-crystal on a four-circle diffractometer, based on the setting angles of reflections, is presented. The minimum information for the determination of crystal displacement are the diffractometer setting angles of two reciprocal vectors. The method is independent of the crystallographic system and does not require prior information about the crystal lattice. The size of the radiation source, beam divergence and homogeneity are shown to be significant factors for calculating the crystal displacement from the positions of the reflections. The method is primarily designed for samples enclosed in high-pressure diamond-anvil cells and other environments obscuring visual control of the sample position; however, high accuracy of the method in most cases allows the optical centering of the crystals to be improved, particularly for irregularly shaped samples. A procedure for retrieving true lattice dimensions, by accounting for the effect of the crystal displacement from the diffractometer center, is also presented.

High-quality structures at high pressure? Insights from inclusions in diamonds

2016 ◽  
Vol 231 (8) ◽  
Author(s):  
Ross J. Angel ◽  
Sula Milani ◽  
Matteo Alvaro ◽  
Fabrizio Nestola
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
High Pressures ◽  
Dominant Factor ◽  
Good Precision ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Experimental Protocols ◽  
Diamond Anvil

AbstractWe describe the experimental protocols necessary to measure the crystal structures of minerals trapped within diamonds by single-crystal X-ray diffraction to the same quality as obtained from minerals studied at ambient conditions. The results show that corrections for X-ray absorption in complex cases can be made with good precision. Comparison of the refined structure of a single-crystal olivine inclusion inside a diamond with the structure of a similar olivine held in a high-pressure diamond-anvil cell shows that data resolution, not the correction for absorption effects, is the dominant factor in influencing the quality of structures determined at high pressures by single-crystal X-ray diffraction.

In situ Raman spectroscopic studies of FeS2 pyrite up to 675 K and 2100 MPa using a hydrothermal diamond anvil cell

2015 ◽  
Vol 79 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Xueyin Yuan ◽  
Haifei Zheng
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Diamond Anvil Cell ◽  
High Pressures ◽  
Quadratic Functions ◽  
Positive Pressure ◽  
Ambient Conditions ◽  
Temperature Conditions ◽  
Diamond Anvil ◽  
Fes2 Pyrite

AbstractRaman scattering experiments of natural FeS2 pyrite were performed at simultaneous high-pressure and high-temperature conditions up to 675 K and 2100 MPa using a hydrothermal diamond anvil cell combined with micro-Raman spectroscopy. Four out of five Raman active modes [Eg, Ag, Tg(1) and Tg(3)] were resolved at ambient conditions, the remaining Tg(2) [∼377 cm–1] mode was weak and unresolved occurring ∼2 cm–1 from the intense Ag [379 cm–1] mode. The frequency shifts of the Eg [343 cm–1] and Ag [379 cm–1] modes were determined to be quadratic functions of pressure and temperature: ν343 = 343.35 – 0.0178 × ΔT – 8.4E – 6 × (ΔT)2 + 0.00367 × Δp 3.7E–7 × (Δp)2 + 1.0E–6 × ΔT × Δp and ν379 = 379.35 – 0.0295 × ΔT – 9.0E–6 × (ΔT)2 + 0.00460 × Δp – 5.3E–7 × (Δp)2 + 7.0E–7 × ΔT × Δp. The positive pressure dependence of both modes indicates stress-induced contraction of S–S and Fe–S bonds, whereas the negative temperature dependence shows temperature-induced expansion of them. The Raman spectra of pyrite were used to derive its bulk modulus at high temperatures, thermal expansion coefficient at high pressures and anharmonic parameters at high-pressure and high-temperature conditions.

A new technique for angle-dispersive powder diffraction using an energy-dispersive setup and synchrotron radiation

2004 ◽  
Vol 37 (6) ◽  
pp. 947-956 ◽  
Author(s):  
Yanbin Wang ◽  
Takeyuki Uchida ◽  
Robert Von Dreele ◽  
Mark L. Rivers ◽  
Norimasa Nishiyama ◽  
...  
Keyword(s):  
High Pressure ◽  
Synchrotron Radiation ◽  
Powder Diffraction ◽  
General Purpose ◽  
Energy Dispersive ◽  
Ambient Conditions ◽  
Energy Bands ◽  
Data Set ◽  
Solid State Detector ◽  
Multiple Data

A new diffraction technique for combined angle- and energy-dispersive structural analysis and refinement (CAESAR), by collecting angle-dispersive data using a solid-state detector (SSD) and white synchrotron radiation, is introduced. By step scanning a well calibrated SSD over a limited 2θ range, a series of one-dimensional energy-dispersive data (intensityversusenergy) are obtained as a function of 2θ. The entire intensity (Int) data set consists of several thousand channels covering a range of photon energies,E(up to ∼150 keV), at each of the ∼1000 2θ steps, forming a 2–4 mega-element two-dimensional array, Int(E, 2θ). These intensity data are then regrouped according to photon energies, which are defined in the multichannel SSD as individual channels, yielding a large number of intensityversus2θ (angle-dispersive) data sets, Int(E= const., 2θ), each of which corresponds to a given photon energy or wavelength. The entire data set, selected subsets or composite scans can be used for multiple data set Rietveld refinement. Data collected both on α-Al2O3(a NIST diffraction standard) at ambient conditions and on a mixture of MgO and Au at high pressure were analyzed using the Rietveld technique, with varying schemes of data treatment. Furthermore, it is demonstrated that data within certain energy bands (ΔE/E= ±10%) may be binned together to improve counting statistics in a composite angle-dispersive scan, even when collected with much coarser scan steps of 0.1 or 0.2°. This technique is useful for high-pressure as well as general purpose powder diffraction studies that have limited X-ray access to the sample using synchrotron radiation. Several advantages are discussed.

scholarly journals High-pressure and environment effects in selenourea and its labile crystal field around molecules

2021 ◽  
Vol 77 (3) ◽  
pp. 449-455
Author(s):  
Kinga Roszak ◽  
Andrzej Katrusiak
Keyword(s):  
High Pressure ◽  
Single Crystals ◽  
Ambient Pressure ◽  
Recrystallization Process ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Environment Effects ◽  
Diamond Anvil ◽  
Trigonal Phase

Ambient-pressure trigonal phase α of selenourea SeC(NH2)2 is noncentrosymmetric, with high Z′ = 9. Under high pressure it undergoes several intriguing transformations, depending on the pressure-transmitting medium and the compression or recrystallization process. In glycerine or oil, α-SeC(NH2)2 transforms into phase β at 0.21 GPa; however in water, phase α initially increases its volume and can be compressed to 0.30 GPa due to the formation of α-SeC(NH2)2·xH2O. The single crystals of α-SeC(NH2)2 and of its partial hydrate α-SeC(NH2)2·xH2O are shattered by pressure-induced transitions. Single crystals of phase β-SeC(NH2)2 were in situ grown in a diamond-anvil cell and studied by X-ray diffraction. The monoclinic phase β is centrosymmetric, with Z′ = 2. It is stable to 3.20 GPa at least, but it cannot be recovered at ambient conditions due to strongly strained NH...Se hydrogen bonds. No hydrogen-bonding motifs present in the urea structures have been found in selenourea phases α and β.

scholarly journals The novel high-pressure/high-temperature compound Co12P7 determined from synchrotron data

2020 ◽  
Vol 76 (10) ◽  
pp. 1665-1668
Author(s):  
Claire Zurkowski ◽  
Barbara Lavina ◽  
Stella Chariton ◽  
Sergey Tkachev ◽  
Vitali Prakapenka ◽  
...  
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
The Novel ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Group Type ◽  
Peak Broadening ◽  
High Pressure High Temperature ◽  
Diamond Anvil ◽  
Laser Heated

The structural properties of cobalt phosphides were investigated at high pressures and temperatures to better understand the behavior of metal-rich phosphides in Earth and planetary interiors. Using single-crystal X-ray diffraction synchrotron data and a laser-heated diamond anvil cell, we discovered a new high pressure–temperature (HP–HT) cobalt phosphide, Co12P7, dodecacobalt heptaphosphide, synthesized at 27 GPa and 1740 K, and at 48 GPa and 1790 K. Co12P7 adopts a structure initially proposed for Cr12P7 (space-group type P\overline{6}, Z =1), consisting of chains of edge-sharing CoP5 square pyramids and chains of corner-sharing CoP4 tetrahedra. This arrangement leaves space for trigonal–prismatic channels running parallel to the c axis. Coupled disordering of metal and phosphorus atoms has been observed in this structure for related M 12P7 (M = Cr, V) compounds, but all Co and P sites are ordered in Co12P7. All atomic sites in this crystal structure are situated on special positions. Upon decompression to ambient conditions, peak broadening and loss of reflections at high angles was observed, suggesting phase instability.

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