scholarly journals Structural and compositional variations of basic Cu(II) chlorides in the herbertsmithite and gillardite structure field

2017 ◽  
Vol 81 (1) ◽  
pp. 123-134
Author(s):  
Matthew J. Sciberras ◽  
Peter Leverett ◽  
Peter A. Williams ◽  
Jochen Schlüter ◽  
Thomas Malcherek ◽  
...  
Keyword(s):  
Single Crystal ◽  
X Ray Diffraction ◽  
Trigonal Symmetry ◽  
X Ray ◽  
Compositional Variations ◽  
End Members

AbstractNatural samples of the substituted basic Cu(II) chloride series, Cu4–xMx2+(OH)6Cl2(M = Zn, Ni, or Mg) were investigated by single-crystal X-ray diffraction in order to elucidate compositional boundaries associated with paratacamite and its congeners. The compositional ranges examined are Cu3.65Zn0.35(OH)6Cl2 – Cu3.36Zn0.64(OH)6Cl2 and Cu3.61Ni0.39(OH)6Cl2 – Cu3.13Ni0.87(OH)6Cl2, along with a single Mg-bearing phase. The majority of samples studied have trigonal symmetry (R3̄m) analogous to that of herbertsmithite (Zn) and gillardite (Ni), with a ≈ 6.8, c ≈ 14.0 Å. Crystallographic variations for these samples caused by composition are compared with both published and new data for the R3̄m sub-cell of paratacamite, paratacamite-(Mg) and paratacamite-(Ni). The observed trends suggest that the composition of end-members associated with the paratacamite congeners depend upon the nature of the substituting cation.

The wulfenite—stolzite series: centric or acentric structures?

2008 ◽  
Vol 72 (4) ◽  
pp. 987-990 ◽  
Author(s):  
L. Secco ◽  
F. Nestola ◽  
A. Dal Negro
Keyword(s):  
Single Crystal ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
End Members ◽  
Symmetry Change

AbstractThree natural crystals of the wulfenite (PbMoO4)—stolzite (PbWO4) series were investigated by single-crystal X-ray diffraction. The results indicate that the symmetry is I41/a from nearly pure wulfenite to intermediate compositions, in contrast to previous work which claimed a symmetry change to 74 symmetry (acentric) for intermediate compositions compared with I41/a (centric space group) for the end-members. The results reported here show that the reflections violating I41/a symmetry observed in this work and in a previous study are related primarily to λ/2 effects, even if Renninger effects are not excluded. Consequently, we find that the I41/a symmetry is retained throughout the wulfenite— stolzite.

scholarly journals High-pressure and high-temperature single-crystal X-ray diffraction of complex garnet solid solutions up to 16 GPa and 823 K

2021 ◽  
Vol 48 (4) ◽  
Author(s):  
Christopher Beyer ◽  
Alexander V. Kurnosov ◽  
Tiziana Boffa Ballaran ◽  
Daniel J. Frost
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Solid Solutions ◽  
Upper Mantle ◽  
Equations Of State ◽  
X Ray Diffraction ◽  
X Ray ◽  
Garnet Composition ◽  
The Difference ◽  
End Members

AbstractP–V–T equations of state (EoS) of synthetic garnet solid solutions with ternary grossular–almandine–pyrope compositions relevant to the Earth’s upper mantle have been determined in order to examine whether garnet properties can be accurately interpolated from those of the end-members. Volumes have been measured as a function of pressure using single-crystal X-ray diffraction measurements performed inside a diamond anvil cell. Isothermal bulk moduli and first pressure derivatives were obtained by fitting the P–V data using a third-order Birch–Murnaghan equation of state. Two nominally eclogitic garnets (Prp47Alm19Grs31And3 and Prp53Alm19Grs18And3Sps7) were found to have isothermal bulk moduli (KT0) and pressure derivatives (K′T0) of 170(3) GPa, 4.1 (4) and 173 (2) GPa, 3.8 (5), respectively. KT0 and K′T0 for an almandine-rich garnet (Prp26Alm63Grs6And5) were found to be 175 (3) GPa and 3.7 (7), respectively. High-temperature compression experiments at 703 K and 823 K were carried out on sample Prp47Alm19Grs31And3, resulting in the high-temperature EoS term (∂KT/∂T)P = − 0.025 (6) and a thermal expansion (α0) of 2.86 (4) × 10−5 K−1. The results imply that the bulk moduli of aluminous garnet solid solutions stable at upper mantle conditions can be deduced from the properties of the end-members with minimal uncertainty. We show that the difference in the bulk sound velocity determined for a multicomponent eclogitic garnet composition and obtained for the same composition from the end-member properties is better than 0.5% for pressures and temperatures corresponding to Earth’s upper mantle.

Local and long-range order in ferroelastic lead phosphate at high pressure

2004 ◽  
Vol 60 (1) ◽  
pp. 1-9 ◽  
Author(s):  
R. J. Angel ◽  
U. Bismayer ◽  
W. G. Marshall
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Single Crystal ◽  
Local Structure ◽  
High Pressures ◽  
X Ray Diffraction ◽  
Lead Phosphate ◽  
Pure Lead ◽  
Trigonal Symmetry ◽  
X Ray

Pure lead phosphate, Pb3(PO4)2, undergoes a phase transition from C2/c to R\bar 3m symmetry at a pressure of approximately 1.8 GPa and room temperature. Single-crystal X-ray diffraction measurements of the unit-cell parameters of a sample doped with 1.6% Ba2+ for the Pb2+ indicates that the doping reduces the transition pressure by approximately 0.1 GPa. The structural evolution of both samples through the phase transition has been determined by Rietveld refinement of neutron powder diffraction data collected to pressures of 6.3 and 3.3 GPa, respectively. There is no evidence for any significant change in the local structure at the phase transition at high pressures; the structure of the R\bar 3m phase at pressures just above the phase transition includes disordered positions for several atoms. The observation of diffuse scattering from the R\bar 3m phase at high pressure by single-crystal X-ray diffraction suggests that the disorder is static and arises from the presence of several orientations of the ordered microdomains of the monoclinic local structure. The macroscopic transition from monoclinic to trigonal symmetry therefore appears to correspond to the pressure at which the coherency strains between the locally monoclinic microdomains are sufficient to create a dimensionally trigonal lattice within which local displacements of atoms are still significant. A further pressure increase then decreases the magnitude of these displacements until at 3.5 GPa or higher they are not detectable by our current experimental probes, and the structure appears to have true local and global trigonal symmetry.

Electron Microscopy of Shock Loaded Polycrystalline Beryllium

1974 ◽  
Vol 32 ◽  
pp. 506-507 ◽  
Author(s):  
J. M. Galbraith ◽  
L. E. Murr ◽  
A. L. Stevens
Keyword(s):  
Electron Microscopy ◽  
Wave Propagation ◽  
Structural Change ◽  
Single Crystal ◽  
Diffraction Pattern ◽  
Shock Loading ◽  
Slip Systems ◽  
Compression Tests ◽  
X Ray Diffraction ◽  
X Ray

Uniaxial compression tests and hydrostatic tests at pressures up to 27 kbars have been performed to determine operating slip systems in single crystal and polycrystal1ine beryllium. A recent study has been made of wave propagation in single crystal beryllium by shock loading to selectively activate various slip systems, and this has been followed by a study of wave propagation and spallation in textured, polycrystal1ine beryllium. An alteration in the X-ray diffraction pattern has been noted after shock loading, but this alteration has not yet been correlated with any structural change occurring during shock loading of polycrystal1ine beryllium.This study is being conducted in an effort to characterize the effects of shock loading on textured, polycrystal1ine beryllium. Samples were fabricated from a billet of Kawecki-Berylco hot pressed HP-10 beryllium.

Microdomains in BaFeO3-y (0.35 < y < 0.50)

1990 ◽  
Vol 48 (4) ◽  
pp. 780-781
Author(s):  
M. Vallet-Regí ◽  
M. Parras ◽  
J.M. González-Calbet ◽  
J.C. Grenier
Keyword(s):  
Electron Diffraction ◽  
Chemical Analysis ◽  
Monoclinic Phase ◽  
Orthorhombic Phase ◽  
Total Iron ◽  
Zone Axis ◽  
Electron Micrograph ◽  
X Ray Diffraction ◽  
X Ray ◽  
Compositional Variations

BaFeO3-y compositions (0.35<y<0.50) have been investigated by means of electron diffraction and microscopy to resolve contradictory results from powder X-ray diffraction data.The samples were obtained by annealing BaFeO2.56 for 48 h. in the temperature range from 980°C to 1050°C . Total iron and barium in the samples were determined using chemical analysis and gravimetric methods, respectively.In the BaFeO3-y system, according to the electron diffraction and microscopy results, the nonstoichiometry is accommodated in different ways as a function of the composition (y):In the domain between BaFeO2.5+δBaFeO2.54, compositional variations are accommodated through the formation of microdomains. Fig. la shows the ED pattern of the BaFeO2.52 material along thezone axis. The corresponding electron micrograph is seen in Fig. 1b. Several domains corresponding to the monoclinic BaFeO2.50 phase, intergrow with domains of the orthorhombic phase. According to that, the ED pattern of Fig. 1a, can be interpreted as formed by the superposition of three types of diffraction maxima : Very strong spots corresponding to a cubic perovskite, a set of maxima due to the superposition of three domains of the monoclinic phase along [100]m and a series of maxima corresponding to three domains corresponding to the orthorhombic phase along the [100]o.

Crystal structure of an inclusion complex between chiral monoaza-15-crown-5 and S(–)-1-phenyl-ethyl ammonium percholorate

2003 ◽  
Vol 218 (5) ◽  
Author(s):  
Süheyla Özbey ◽  
F. B. Kaynak ◽  
M. Toğrul ◽  
N. Demirel ◽  
H. Hoşgören
Keyword(s):  
Crystal Structure ◽  
Inclusion Complex ◽  
Single Crystal ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
New Type

AbstractA new type of inclusion complex, S(–)-1 phenyl ethyl ammonium percholorate complex of R-(–)-2-ethyl - N - benzyl - 4, 7, 10, 13 - tetraoxa -1- azacyclopentadecane, has been prepared and studied by NMR, IR and single crystal X-ray diffraction techniques. The compound crystallizes in space group

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