Synthesis and crystal structure refinement by the Rietveld method of antimony-bearing titanite Ca(Ti0.6Al0.2Sb0.2)OSiO4

2009 ◽  
Vol 24 (3) ◽  
pp. 221-227
Author(s):  
Fernando Colombo ◽  
Elisa V. Pannunzio Miner
Keyword(s):  
Crystal Structure ◽  
Long Range ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Unit Cell ◽  
Synthetic Analogue ◽  
Crystal Structure Refinement ◽  
Synthesis And Crystal Structure ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

A synthetic analogue, Ca(Ti0.6Al0.2Sb0.2)OSiO4, of antimony-bearing titanite of a composition similar to that found at St. Marcel-Praborna (Italy) was synthesized using ceramic methods and the crystal structure was refined using the Rietveld method. Unit-cell dimensions (in Å) are a=7.0184(1), b=8.7097(2), c=6.5586(1), and β=113.700(1)°. The substitution of 40% Ti by (Al+Sb) in octahedra causes a loss of long-range coherency of the off-centered Ti atoms. The space group of Sb-bearing titanite is A2/a, like other cases of M3+-M5+-doped titanites. This study confirms that titanite with up to 0.2 Sb atom per f.u. can exist and that the substitution scheme is 2Ti4+↔Al3++Sb5+.

scholarly journals Nickelphosphide from the Vicenice octahedrite: Rietveld crystal structure refinement of a synthetic analogue

2003 ◽  
Vol 67 (4) ◽  
pp. 783-792 ◽  
Author(s):  
R. Skála ◽  
M. Drábek
Keyword(s):  
Crystal Structure ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Original Description ◽  
Synthetic Analogue ◽  
Synthetic Compounds ◽  
Structure Information ◽  
Profile Fitting ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

AbstractThe original description of nickelphosphide from the Butler meteorite [(Ni1.83Fe1.21)Σ3.04P0.96 to (Ni1.71Fe1.28Co0.01)Σ3.00P1.00] lacks detailed and accurate powder data – with only 11 observed reflections down to 1.37 Å. Consequently, no crystal structure information for this phase is available. Here we present the crystal structure for a synthetic analogue of the phase found in the Vicenice IID medium octahedrite (with a mean empirical formula of (Ni1.69Fe1.31)Σ3.00P1.00) and a hypothetical Ni3P end-member. Unit-cell dimensions of the synthetic analogue of Ni1.68Fe1.33P0.99 composition from individual peak profile fitting of XRD data collected with Cu radiation are a= 9.0168(2)Å, c= 4.4491(1)Å, V= 361.72(1)Å3 and those for Ni3P composition are a= 8.9546(1)Å, c= 4.38714(8)Å, V= 351.783(8)Å3. The space group of the mineral is I4¯ and Z= 8. The crystal structure refined from powder data by the Rietveld method is consistent with that refined and published for Fe3P and Ni3P synthetic compounds as well as Fe-dominant schreibersite from single-crystal data. However, because of the similarity of the scattering of iron and nickel, we were not able to refine directly the site occupancies in the synthetic analogue of the nickelphosphide from the Vicenice iron meteorite.

Synthesis and crystal structure of Na3.5Cr1.5Co0.5(PO4)3 phosphate

2006 ◽  
Vol 21 (3) ◽  
pp. 210-213 ◽  
Author(s):  
Mohamed Chakir ◽  
Abdelaziz El Jazouli ◽  
Jean-Pierre Chaminade
Keyword(s):  
Crystal Structure ◽  
Three Dimensional ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
Space Group ◽  
X Ray ◽  
Hexagonal Unit Cell ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

A new Nasicon phosphates series [Na3+xCr2−xCox(PO4)3(0⩽x⩽1)] was synthesized by a coprecipitation method and structurally characterized by powder X-ray diffraction. The selected compound Na3.5Cr1.5Co0.5(PO4)3 (x=0.5) crystallizes in the R3c space group with the following hexagonal unit-cell dimensions: ah=8.7285(3) Å, ch=21.580(2) Å, V=1423.8(1) Å3, and Z=6. This three-dimensional framework is built of PO4 tetrahedra and Cr∕CoO6 octahedra sharing corners. Na atoms occupy totally M(1) sites and partially M(2) sites.

Magnesio-arfvedsonite from Jade Mine Tract, Myanmar: mineral description and crystal chemistry

2015 ◽  
Vol 79 (2) ◽  
pp. 253-260 ◽  
Author(s):  
Roberta Oberti ◽  
Massimo Boiocchi ◽  
Frank C. Hawthorne ◽  
Neil A. Ball ◽  
George E. Harlow
Keyword(s):  
Crystal Structure ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
American Museum ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
The Ideal

AbstractMagnesio-arfvedsonite, theCFe3+-dominant analogue of eckermannite, has been found in a sample of “szechenyite” in the mineral collection of the American Museum of Natural History (AMNH H35024). It comes from the northern part of the Jade Mine Tract near Hpakan, Kachin State, Myanmar. Associated minerals are kosmochlor–jadeite solid-solution pyroxene and clinochlore. The ideal formula of magnesio-arfvedsonite isANaBNa2C(Mg4Fe3+)TSi8O22W(OH)2, and the empirical formula derived from electron microprobe analysis and single-crystal structure refinement for the sample of this work isA(Na0.96K0.04)Σ=1.00B(Na1.57Ca0.40Fe0.022+Mn0.01)Σ=2.00C(Mg4.26Fe0.192+Fe0.413+Al0.11Ti0.034+)Σ=5.00T(Si7.99Al0.01)Σ=8.00O22W[F0.02(OH)1.98]Σ=2.00. The unit-cell dimensions area= 9.867(1),b= 17.928(2),c= 5.284(1) Å, β = 103.80(2)°,V= 907.7 (2) Å3,Z= 2. Magnesio-arfvedsonite is biaxial (–), with α = 1.624, β = 1.636, γ = 1.637, all ± 0.002 and 2Vobs= 36(1)°, 2Vcalc= 32°. The ten strongest reflections in the X-ray powder pattern [dvalues (in Å),I, (hkl)] are: 2.708, 100, (151); 3.399, 68, (131); 3.144, 63, (310); 2.526, 60, (202); 8.451, 46, (110); 3.273, 39, (240); 2.167, 37, (261); 2.582, 34, (061); 2.970, 34, (221); 2.326, 33, [(251) (421)].

Crystal structure of potassium tetraperoxomolybdate (VI) K2[Mo(O2)4]

2005 ◽  
Vol 20 (3) ◽  
pp. 203-206 ◽  
Author(s):  
M. Grzywa ◽  
M. Różycka ◽  
W. Łasocha
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters

Potassium tetraperoxomolybdate (VI) K2[Mo(O2)4] was prepared, and its X-ray powder diffraction pattern was recorded at low temperature (258 K). The unit cell parameters were refined to a=10.7891(2) Å, α=64.925(3)°, space group R−3c (167), Z=6. The compound is isostructural with potassium tetraperoxotungstate (VI) K2[W(O2)4] (Stomberg, 1988). The sample of K2[Mo(O2)4] was characterized by analytical investigations, and the results of crystal structure refinement by Rietveld method are presented; final RP and RWP are 9.79% and 12.37%, respectively.

Reexamination of the crystal structure of semseyite, Pb9Sb8S21

2018 ◽  
Vol 233 (3-4) ◽  
pp. 279-284 ◽  
Author(s):  
Yoshitaka Matsushita
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Single Crystal ◽  
Structure Refinement ◽  
Unit Cell ◽  
Crystal Structure Refinement ◽  
Cell Level ◽  
Single Crystal Specimen ◽  
Cation Sites ◽  
Occupancy Behavior

AbstractThe crystal structure of semseyite, Pb9Sb8S21was successfully refined using a single-crystal specimen from Wolfsberg, Harz, Germany, having chemical composition (EPMA) Pb9.01(1)Sb8.00(3)S21.05(5). The structure belongs to the monoclinicC2/cspace group (a=13.6267(10) Å,b=11.9742(9) Å,c=24.5891(18) Å,β=105.997(3)°,V=3856.8(5) Å3,Z=4,Dc=6.048 g/cm3). Crystal structure refinement with all atoms refined anisotropically converged toR1=4.64% (I>2σ(I)). The crystal structure is built of two subunits (A and B) showing TlSbS2-like topology. Each of them stacks parallel to (001), andc/2 in thickness. Two cation sites (Pb1 and Sb5) located at central part of the subunit, show mixed occupancy behavior as 95% Pb and 5% Sb at the Pb5 site, and 95% Sb and 5% Pb at the Sb1 site, respectively. Each of subunits are related by unit cell-level twinning mechanism “tropochemical cell twinning” with the TlSbS2-like subunits alternatively parallel to (1 1 −4) and (−1 1 4) planes.

Crystal structures of phenacylkojate (2-(hydroxymethyl)-5-phenacyloxy-4H-pyran-4-one) and its complex with sodium chloride: bis(phenacylkojate)sodium chloride

1976 ◽  
Vol 54 (17) ◽  
pp. 2723-2732 ◽  
Author(s):  
Simon E. V. Phillips ◽  
James Trotter
Keyword(s):  
Crystal Structure ◽  
Sodium Chloride ◽  
Potassium Iodide ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Hydroxyl Groups ◽  
Space Group ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Iodide Complex

The structures of the title compounds have been determined by three dimensional X-ray crystal structure analysis.Crystals of anhydrous phenacylkojate are monoclinic, space group P21/c, with unit cell dimensions a = 9.087(4), b = 11.764(3), c = 12.714(4) Å, β = 116.57(2)°, Z = 4. The structure was solved by direct methods and refined by full-matrix least-squares to R = 0.044 for 1225 independent diffractometer observations. The crystal structure is held together by hydrogen bonding between carbonyl and hydroxyl groups and [Formula: see text] interactions.Crystals of the sodium chloride complex are monoclinic, space group C2/c, with unit cell dimensions a = 11.3714(6), b = 15.796(1), c = 14.487(1) Å, β = 97.241(5)°, Z = 4. The structure was solved by heavy atom and Fourier methods and comparison with the previously determined structure of the potassium iodide complex. It was refined to R = 0.040 for 1670 independent diffractometer observations. The structure closely resembles that of the potassium iodide complex (P21/n), but in C2/c, the alkali metal ion being eight co-ordinate in each. Na+—O distances are in the range 2.558–2.674 Å and the [Formula: see text] hydrogen bonded distance is 3.266 Å.

Water-based sol–gel synthesis and crystal structure refinement of lanthanum silicate apatite

2008 ◽  
Vol 179 (38) ◽  
pp. 2209-2215 ◽  
Author(s):  
K KOBAYASHI ◽  
Y MATSUSHITA ◽  
N IGAWA ◽  
F IZUMI ◽  
C NISHIMURA ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structure Refinement ◽  
Sol Gel ◽  
Crystal Structure Refinement ◽  
Synthesis And Crystal Structure ◽  
Water Based ◽  
Sol Gel Synthesis ◽  
Lanthanum Silicate

Refinement of the structure of Mg2As2O7

1970 ◽  
Vol 48 (6) ◽  
pp. 890-894 ◽  
Author(s):  
C. Calvo ◽  
K. Neelakantan
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Least Squares ◽  
Unit Cell ◽  
Full Matrix ◽  
Space Group ◽  
Cell Dimensions ◽  
Central Oxygen ◽  
R Value ◽  
Unit Cell Dimensions

The crystal structure of Mg2As2O7 has been refined by full matrix least squares procedures using 587 observed reflections. The structure of Mg2As2O7 is of the thortveitite type, as reported by Łukaszewicz, with space group C2/m and unit cell dimensions a = 6.567(2) Å, b = 8.524(4) Å, c = 4.739(1) Å, β = 103.8(1)°, and Z = 2. The As—O—As group in the anion appears to be linear but the central oxygen atom undergoes considerable disorder in the plane perpendicular to this group. The AsO bond distances uncorrected for thermal motion are 1.67 Å for the As—O(—As) bond and 1.66 and 1.65 Å for the terminal As—O bonds. The final R value obtained is 0.088.

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