First-Principles Studies of Pentaerythritol Tetranitrate (PETN) Single Crystal Unit Cell Volumes and Vibrational Frequencies under Hydrostatic Pressure

2006 ◽  
Author(s):  
Warren F. Perger
Keyword(s):  
Hydrostatic Pressure ◽  
Single Crystal ◽  
First Principles ◽  
Vibrational Frequencies ◽  
Unit Cell ◽  
Pentaerythritol Tetranitrate ◽  
Crystal Unit Cell ◽  
Cell Volumes

scholarly journals The Crystal Chemistry of Rathite Based on New Electron-Microprobe Data and Single-Crystal Structure Refinements: The Role of Thallium

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 466
Author(s):  
Dan Topa ◽  
Uwe Kolitsch
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Chemistry ◽  
Electron Microprobe ◽  
Mean Value ◽  
Unit Cell ◽  
Complex Spectrum ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Crystal Unit Cell

Crystal-structure refinements in space group P21/c were performed on five grains of rathite with different types and degrees of thallium, silver, and antimony substitutions, as well as quantitative electron-microprobe analyses of more than 800 different rathite samples. The results of these studies both enlarged and clarified the complex spectrum of cation substitutions and the crystal chemistry of rathite. The [Tl+ + As3+] ↔ 2Pb2+ scheme of substitution acts at the structural sites Pb1, Pb2, and Me6, the [Ag+ + As3+] ↔ 2Pb2+ substitution at Me5, and the Sb-for-As substitution at the Me3 site only. The homogeneity range of rathite was determined to be unusually large, ranging from very Tl-poor compositions (0.16 wt%; refined single-crystal unit-cell parameters: a = 8.471(2), b = 7.926(2), c = 25.186(5) Å, β = 100.58(3)°, V = 1662.4(6) Å3) to very Tl-rich compositions (11.78 wt%; a = 8.521(2), b = 8.005(2), c = 25.031(5) Å, β = 100.56(3)°, V = 1678.4(6) Å3). The Ag content is only slightly variable (3.1 wt%–4.1 wt%) with a mean value of 3.6 wt%. The Sb content is strongly variable (0.20 wt%–7.71 wt%) and not correlated with the Tl content. With increasing Tl content (0.16 wt%–11.78 wt%), a clear increase of the unit-cell parameters a, b, and V, and a slight decrease of c is observed, although this is somewhat masked by the randomly variable Sb content. The revised general formula of rathite may be written as AgxTlyPb16−2(x+y)As16+x+y−zSbzS40 (with 1.6 < x < 2, 0 < y < 3, 0 < z < 3.5). Based on Pb–S bond lengths, polyhedral characteristics and Pb-site bond-valence sums, we conclude that the Pb1 site is more affected by Tl substitution than the Pb2 site. When Tl substitution reaches values above 13 wt% (or 3 apfu), a new phase (“SR”), belonging to the rahite group, appears as lamellar exsolution intergrowths with Tl-rich rathite (11.78 wt%). Rathite is found only in the Lengenbach and Reckibach deposits, Binntal, Canton Wallis, Switzerland.

Structure and bonding in crystalline cesium uranyl tetrachloride under pressure

2016 ◽  
Vol 18 (27) ◽  
pp. 18398-18405 ◽  
Author(s):  
Hussien H. Osman ◽  
Pilar Pertierra ◽  
Miguel A. Salvadó ◽  
F. Izquierdo-Ruiz ◽  
J. M. Recio
Keyword(s):  
Hydrostatic Pressure ◽  
Bond Length ◽  
First Principles ◽  
Vibrational Frequencies ◽  
Structure And Bonding

First-principles simulations of Cs2UO2Cl4 under hydrostatic pressure reveal an unexpected variation of the U–O bond length and stretching vibrational frequencies.

scholarly journals Crystal-Chemical Properties of Synthetic Almandine-Pyrope Solid Solution by X-Ray Single-Crystal Diffraction and Raman Spectroscopy

Crystals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 541 ◽  
Author(s):  
Kuang ◽  
Xu ◽  
Li ◽  
Ye ◽  
Huang ◽  
...  
Keyword(s):  
Solid Solution ◽  
Single Crystal ◽  
Cell Parameter ◽  
Chemical Properties ◽  
Unit Cell ◽  
Crystal Chemical ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Sio4 Tetrahedron ◽  
Crystal Unit Cell

Crystal-chemical properties of synthetic Almandine-Pyrope (Alm-Pyr) solid solutions were investigated by X-ray single-crystal diffraction and Raman spectroscopy. Garnet solid solution with different compositions were synthesized from powder at 4.0 GPa and annealed at 1200 °C for 48 h by a multi-anvil pressure apparatus. Garnet crystals with different sizes (about 60-1000 μm) were obtained from synthesis. The results of X-ray single-crystal diffraction show that the unit cell constants decrease with increasing Pyr contents in the synthetic Alm-Pyr crystals due to the smaller ionic radius of Mg2+ in eightfold coordination than that of Fe2+. The data exhibit obviously positive deviations from ideal mixing volumes across the Alm-Pyr join which may be caused by the distortion of the SiO4 tetrahedron. Moreover, the significant decrease in the average M-O bond length and volume of the [MgO8]/[FeO8] dodecahedron with increasing Pyr contents are the most important factors to the decrease in the Alm-Pyr crystal unit cell constant and volume. On the other hand, selected bond distances (average <M-O>, <Al-O>, and <D-O> distances) have a linear correlation with the unit-cell parameter, but the <Si-O> distance has nonlinear correlation. With increasing the unit-cell parameter, the average <M-O> distance increases significantly, followed by the average <D-O> and <Al-O> distances. While the <Si-O> distance changes negligibly further confirming the conclusion that the significant decrease of the average M-O bond length of the [MgO8]/[FeO8] dodecahedron with increasing Pyr contents are the most important factors to the decrease in the Alm-Pyr crystal unit cell volume. In the Raman spectra collected for the Alm-Pyr solid solutions, Raman vibration mode assignments indicate that the Raman vibrational spectra change along the Alm-Pyr binary solution. The mode frequencies of Si-O stretching, Si-O bending, and the rotation of the SiO4-tetrahedron (R(SiO4)) decrease linearly, while the translational modes of the SiO4-tetrahedron (T(SiO4)) increase with increasing Alm contents.

Fabrication and study the effect of the laser on the properties of the compound Tl2-xHgxBa2-ySryCa2Cu3O10+δ superconductor

2018 ◽  
pp. 168
Author(s):  
A. Kareem Dahash Ali ◽  
Nihad Ali Shafeek
Keyword(s):  
Transition Temperature ◽  
Solid State ◽  
Hydrostatic Pressure ◽  
Electrical Properties ◽  
Co2 Laser ◽  
Temperature Shift ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural And Electrical Properties

This study included the fabrication of    compound (Tl2-xHgxBa2-ySryCa2Cu3O10+δ) in a manner solid state and under hydrostatic pressure ( 8 ton/cm2) and temperature annealing(850°C), and determine the effect of the laser on the structural and electrical properties elements in the compound, and various concentrations of x where (x= 0.1,0.2,0.3 ). Observed by testing the XRD The best ratio of compensation for x is 0.2 as the value of a = b = 5.3899 (A °), c = 36.21 (A °) show that the installation of four-wheel-based type and that the best temperature shift is TC= 142 K  .When you shine a CO2 laser on the models in order to recognize the effect of the laser on these models showed the study of X-ray diffraction of these samples when preparing models with different concentrations of the values ​​of x, the best ratio of compensation is 0.2 which showed an increase in the values ​​of the dimensions of the unit cell a=b = 5.3929 (A °), c = 36.238 (A°). And the best transition temperature after shedding laser is TC=144 K. 

scholarly journals Intrinsic Properties ofAFe2As2(A= Ba, Sr) Single Crystal under Highly Hydrostatic Pressure Conditions

2009 ◽  
Vol 78 (7) ◽  
pp. 073706 ◽  
Author(s):  
Kazuyuki Matsubayashi ◽  
Naoyuki Katayama ◽  
Kenya Ohgushi ◽  
Atsushi Yamada ◽  
Koji Munakata ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Single Crystal ◽  
Intrinsic Properties
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