scholarly journals Structural Assessment of Fluorine, Chlorine, Bromine, Iodine, and Hydroxide Substitutions in Lead Arsenate Apatites (Mimetites)–Pb5(AsO4)3X

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 494
Author(s):  
Julia Sordyl ◽  
Bartosz Puzio ◽  
Maciej Manecki ◽  
Olaf Borkiewicz ◽  
Justyna Topolska ◽  
...  
Keyword(s):  
Rietveld Refinement ◽  
Twist Angle ◽  
Interatomic Distances ◽  
Cell Parameters ◽  
Lead Arsenate ◽  
Comparable Effect ◽  
Comparison Of The Results ◽  
Symmetry Space ◽  
Linear Correlations ◽  
Symmetry Space Group

Five lead-arsenate apatites (mimetites)-Pb5(AsO4)3X—where X denotes fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and hydroxide (OH)—were synthesized via precipitation from aqueous solutions. The crystal structures were determined through Rietveld refinement of powder synchrotron X-ray data. All the compounds crystallized in the hexagonal class symmetry (space group P63/m). The Rietveld refinement indicated that mimetite-Cl, -Br, -I, and -OH had an anion deficiency at position X. Substitution of halogens in a mimetite structure brought about systematic changes in unit-cell parameters, interatomic distances, and metaprism twist angles φ, proportional to the substituted halogen’s ionic radius. Mimetite-OH did not follow the linear correlations determined within the series. Twist angle φ, a useful device for monitoring changes in apatite topology, ranged from 20.34° for mimetite-F to 11.42° for mimetite-I. The geometric method has been proposed for determining the diameter of hexagonal channels hosting halogens in apatites. A comparison of the results with halogenated pyromorphites showed similar systematic trends: the substitutions in mimetites have comparable effect on the interatomic distances as in their phosphorous analogues.

scholarly journals X-ray powder diffraction analysis of a silver(I) cyclamate complex

2007 ◽  
Vol 22 (1) ◽  
pp. 68-70
Author(s):  
R. Putvinskis ◽  
C. O. Paiva Santos ◽  
M. Cavicchioli ◽  
A. C. Massabni
Keyword(s):  
Powder Diffraction ◽  
Powder Diffraction Data ◽  
Stoichiometric Mixture ◽  
Unit Cell Parameters ◽  
Monoclinic Symmetry ◽  
X Ray ◽  
Cell Parameters ◽  
Sodium Cyclamate ◽  
Symmetry Space ◽  
Symmetry Space Group

X-ray powder diffraction data collected for the complex silver(I) cyclamate [Ag(C6H12NO3S)] are reported. This material was obtained from a stoichiometric mixture of sodium cyclamate and AgNO3. The analysis of the data using the Le Bail method showed that the complex has monoclinic symmetry (space group C2/c). The unit cell parameters are a=31.85852(16) Å, b=6.25257(6) Å, c=8.46165(7) Å, and β=95.7651(5)°.

scholarly journals Hydroxycalciomicrolite, Ca1.5Ta2O6(OH), a new member of the microlite group from Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil

2017 ◽  
Vol 81 (3) ◽  
pp. 555-564 ◽  
Author(s):  
M. B. Andrade ◽  
H. Yang ◽  
D. Atencio ◽  
R. T. Downs ◽  
N. V. Chukanov ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Minas Gerais ◽  
Calculated Density ◽  
Group Mineral ◽  
Cell Parameters ◽  
Mohs Hardness ◽  
Long Range Ordering ◽  
Symmetry Space ◽  
Symmetry Space Group

AbstractHydroxycalciomicrolite, Ca1.5Ta2O6(OH) is a new microlite-group mineral found in the Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil. It occurs as isolated octahedral and as a combination of octahedral and rhombic dodecahedral crystals, up to1.5 mm in size. The crystals are yellow and translucent, with a white streak and vitreous to resinous lustre. The mineral is brittle, with a Mohs hardness of 5–6. Cleavage is not observed and fracture is conchoidal. The calculated density is 6.176 g cm–3. Hydroxycalciomicroliteis isotropic,ncalc.= 2.010. The infrared and Raman spectra exhibit bands due to O–H stretching vibrations. The chemical composition determined from electron microprobe analysis (n= 13) is (wt.%): Na2O 0.36(8), CaO 15.64(13), SnO20.26(3),Nb2O52.82(30), Ta2O578.39(22), MnO 0.12(2), F 0.72(12) and H2O 1.30 (from the crystal structure data), O = F –0.30, total 99.31(32), yielding an empirical formula, (Ca1.48Na0.06Mn0.01)∑1.55(Ta1.88Nb0.11Sn0.01)∑2.00O6.00[(OH)0.76F0.20O0.04].Hydroxycalciomicrolite is cubic, with unit-cell parametersa= 10.4205(1) Å,V= 1131.53(2) Å3andZ= 8. It represents a pyrochlore supergroup, microlite-group mineral exhibitingP4332 symmetry, instead ofFd3m. Thereduction in symmetry is due to long-range ordering of Ca and vacancies on theAsites. This is the first example of such ordering in a natural pyrochlore, although it is known from synthetic compounds. This result is promising because it suggests that other species withP4332or lower-symmetry space group can be discovered and characterized.

Schmidite and wildenauerite, two new schoonerite-group minerals from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria

2018 ◽  
Vol 83 (02) ◽  
pp. 181-190
Author(s):  
Ian E. Grey ◽  
Erich Keck ◽  
Anthony R. Kampf ◽  
John D. Cashion ◽  
Colin M. MacRae ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Tetrahedral Site ◽  
Orthorhombic Symmetry ◽  
Charge Balance ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Symmetry Space ◽  
Symmetry Space Group

AbstractSchmidite, Zn(Fe3+0.5Mn2+0.5)2ZnFe3+(PO4)3(OH)3(H2O)8 and wildenauerite, Zn(Fe3+0.5Mn2+0.5)2Mn2+Fe3+(PO4)3(OH)3(H2O)8 are two new oxidised schoonerite-group minerals from the Hagendorf-Süd pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Schmidite occurs as radiating sprays of orange–brown to copper-red laths on and near to altered phosphophyllite in a corroded triphylite nodule, whereas wildenauerite forms dense compacts of red laths, terminating Zn-bearing rockbridgeite. The minerals are biaxial (+) with α = 1.642(2), β = 1.680(1), γ = 1.735(2) and 2Vmeas = 81.4(8)° for schmidite, and with α = 1.659(3), β = 1.687(3), γ = 1.742(3) and 2Vmeas = 73(1)° for wildenauerite. Electron microprobe analyses, with H2O from thermal analysis and FeO/Fe2O3 from Mössbauer spectroscopy, gave FeO 0.4, MgO 0.3, Fe2O3 23.5, MnO 9.0, ZnO 15.5, P2O5 27.6, H2O 23.3, total 99.6 wt.% for schmidite, and FeO 0.7, MgO 0.3, Fe2O3 25.2, MnO 10.7, ZnO 11.5, P2O5 27.2, H2O 24.5, total 100.1 wt.% for wildenauerite. The empirical formulae, scaled to 3 P and with OH– adjusted for charge balance are Zn1.47Mn2+0.98Mg0.05Fe2+0.04Fe3+2.27(PO4)3(OH)2.89(H2O)8.54 for schmidite and Zn1.11Mn2+1.18Mg0.05Fe2+0.08Fe3+2.47(PO4)3(OH)3.25(H2O)9.03 for wildenauerite. The two minerals have orthorhombic symmetry, space group Pmab and Z = 4. The unit-cell parameters from refinement of powder X-ray diffraction data are a = 11.059(1), b = 25.452(1) and c = 6.427(1) Å for schmidite, and a = 11.082(1), b = 25.498(2) and c = 6.436(1) Å for wildenauerite. The crystal structures of schmidite and wildenauerite differ from that of schoonerite in having minor partitioning of Zn from the [5]Zn site to an adjacent vacant tetrahedral site [4]Zn, separated by ~1.0 Å from [5]Zn. The two minerals are distinguished by the cation occupancies in the octahedral M1 to M3 sites. Schmidite has M1 = M2 = (Fe3+0.5Mn2+0.5) and M3 = Zn and wildenauerite has M1 = M2 = (Fe3+0.5Mn2+0.5) and M3 = Mn2+.

Zur Kristallchemie des ersten Blei-Zink-Silicium-Telluroxids: PbZn4SiTeO10 / On the Crystal Chemistry of the First Lead Zinc Silicon Tellurium Oxyde PbZn4SiTeO10

1999 ◽  
Vol 54 (4) ◽  
pp. 469-472 ◽  
Author(s):  
B. Wedel ◽  
K. Sugiyama ◽  
K. Hiraga ◽  
K. Itagaki
Keyword(s):  
Negative Charge ◽  
Lattice Energy ◽  
Orthorhombic Symmetry ◽  
X Ray ◽  
Cell Parameters ◽  
Coulomb Term ◽  
Lead Zinc ◽  
Group D ◽  
Symmetry Space ◽  
Symmetry Space Group

Single crystals of the new lead zinc silicon tellurium oxide PbZn4SiTeO10 have been prepared by solid state reaction in air. The compound is colourless and crystallizes in orthorhombic symmetry, space group D162h Pnma, with the cell parameters: a = 6.542 (5), b = 15.624(4), c = 8.280(4) Å, Z = 4. The structure has been determined from a single crystal X-ray study and refined to the conventional values R = 0.032 and wR(F2) = 0.050. Zn2+ and Si4+ show tetrahedral and Te6+ octahedral coordination by O2-.The crystal structure is dominated by a 3∞ [Zn4O10]12- framework with isolated TeO66+ and SiO44+ polyhedra. Pb2+ ions are incorporated in the network. The centres of negative charge of the lone pairs of Pb2+ are estimated by calculations of the Coulomb term of the lattice energy

Pure, lithium- or magnesium-doped ferroelectric single crystals of Ca9Y(VO4)7: cation arrangements and phase transitions

2018 ◽  
Vol 233 (7) ◽  
pp. 453-462 ◽  
Author(s):  
Bogdan I. Lazoryak ◽  
Dina V. Deyneko ◽  
Sergey M. Aksenov ◽  
Sergey Yu. Stefanovich ◽  
Elena A. Fortalnova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Single Crystals ◽  
Czochralski Method ◽  
Paraelectric Phase Transition ◽  
Cell Parameters ◽  
Structure Changes ◽  
Ferroelectric Phase Transitions ◽  
Symmetry Space ◽  
Symmetry Space Group

Abstract Single crystals of Ca9Y(VO4)7 (1), Ca9Y(VO4)7:Li+ (2) and Ca9Y(VO4)7:Mg2+ (3) were grown by the Czochralski method. Their chemical composition was analyzed by ICP spectroscopy and their crystal structure was examined by single crystal X-ray analysis. The crystals are characterized by trigonal symmetry, space group R3c. Hexagonal unit-cell parameters are as follows: a=10.8552(1) Å, c=38.0373(2) Å, V=3881.65(1) Å3 for 1; a=10.8570(1) Å, c=38.0161(3) Å, V=3880.77(4) Å3 for 2; a=10.8465(1) Å, c=38.0366(2) Å, V=3875.36(3) Å3 for 3. All crystals are characterized by β-Ca3(PO4)2-type structure with statistical distribution of Ca2+ and Y3+ over M1, M2 and M5 sites in different ratios and with completely empty M4-cationsite. The impurity of Mg2+cations in structure 2 has been detected in octahedral M5 site. Ferroelectric phase transitions are evidenced by DSC and SHG. At about 1220 and 1300 K, they demonstrate phase transitions. Upon heating the symmetry of the crystal structure changes according to the scheme R3c→R3̅c→R3̅m and is restored during consequent cooling. The first of them is of ferroelectric and the second of non-ferroelectric nature. Even a small amount of impurities in Ca9Y(VO4)7 structure is accompanied by a noticeable decrease in the temperature of the ferroelectric-paraelectric phase transition.

Oxo-magnesio-hastingsite, NaCa2(Mg2Fe3+3 )(Al2Si6)O22O2, a new anhydrous amphibole from the Deeti volcanic cone, Gregory rift, northern Tanzania

2013 ◽  
Vol 77 (6) ◽  
pp. 2773-2792 ◽  
Author(s):  
A. N. Zaitsev ◽  
E. Yu. Avdontseva ◽  
S. N. Britvin ◽  
A. Demény ◽  
Z. Homonnay ◽  
...  
Keyword(s):  
Chemical Formula ◽  
Unit Cell Parameters ◽  
Monoclinic Symmetry ◽  
Water Determination ◽  
Volcanic Cone ◽  
Cell Parameters ◽  
Northern Tanzania ◽  
Symmetry Space ◽  
Symmetry Space Group ◽  
Measured Density

AbstractOxo-magnesio-hastingsite, ideally NaCa2(Mg2Fe3+3)(Al2Si6)O22O2, is a new anhydrous amphibole from the Deeti volcanic cone in the Gregory rift (northern Tanzania). The mineral occurs as megacrysts up to 12 cm in size in crystal-rich tuff. Oxo-magnesio-hastingsite is brown with a vitreous lustre and has a perfect {110} cleavage. The measured density is 3.19(1) g/cm3. Ferri-kaersutite is biaxial (–), α = 1.706 (2), β = 1.715(2), γ = 1.720(2) (Na light, 589 nm). 2V (calc.) = 73°. Dispersion: r > v, weak; orientation: Y = b; Z ^ c = 8°; pleochroism: strong, Z: dark brown, Y: brown, X: light brown. The average chemical formula of the mineral derived from electron microprobe analyses, Mössbauer spectroscopy and direct water determination is (Na0.67K0.33)Σ1.00(Ca1.87Na0.14Mn0.01)Σ2.02(Mg3.27Fe3+1.25Ti0.44Al0.08)Σ5.04(Al1.80Si6.20O22)(O1.40OH0.60)Σ2.00. It has monoclinic symmetry, space group C2/m and unit-cell parameters a = 9.8837(3), b = 18.0662(6), c = 5.3107(2) Å, b = 105.278(1)o, V = 914.77(5) Å3, Z = 2. The five strongest powder-diffraction lines [d in Å, (I/Io), hkl] are: 3.383 (62) (131), 2.708 (97) (151), 2.555 (100) (), 2.349 (29) () and 2.162 (36) (261). The isotopic composition of H and O, as well as the concentration of trace elements in oxo-magnesio-hastingsite suggest its formation from a melt originated from a mantle source metasomatized by slab-derived fluids.

Powder diffraction data for niobium IV hexafluorides: VNbF6 and CrNbF6

1998 ◽  
Vol 13 (3) ◽  
pp. 132-133
Author(s):  
Fabrice Goubard ◽  
Daniel Bizot ◽  
Jean Chassaing
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Tetragonal Symmetry ◽  
Powder Diffraction Data ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Cell Parameters ◽  
High Temperature Form ◽  
Symmetry Space ◽  
Symmetry Space Group

New hexafluoroniobates IV, VNbF6 and the high-temperature form of CrNbF6 have been synthesized by solid-state reaction. The former is isostructural with rhombohedral LiSbF6, space group R3¯, and the latter crystallizes with tetragonal symmetry, space group I/4mmm. Unit-cell parameters were determined: a=5.520(1) Å, c=13.987(5) Å, V=369.0(1) Å3, Z=3 for VNbF6, and a=5.5403(5) Å, c=8.453(1) Å, V=259.5(1) Å3, Z=2 for the “HT” form of CrNbF6. Powder diffraction data are reported.

Chiral edge-shared octahedral chains in liskeardite, [(Al,Fe)32(AsO4)18(OH)42(H2O)22]·52H2O, an open framework mineral with a pharmacoalumite-related structure

2013 ◽  
Vol 77 (8) ◽  
pp. 3125-3135 ◽  
Author(s):  
I. E. Grey ◽  
W. G. Mumme ◽  
C. M. Macrae ◽  
T. Caradoc-Davies ◽  
J. R. Price ◽  
...  
Keyword(s):  
Structure Refinement ◽  
Type Specimen ◽  
Close Packing ◽  
Cell Parameters ◽  
Open Framework ◽  
Structural Relationships ◽  
Diameter Fibre ◽  
Cation Sites ◽  
Symmetry Space ◽  
Symmetry Space Group

AbstractThe type specimen of liskeardite, (Al, Fe)3AsO4(OH)6·5H2O, from the Marke Valley Mine, Liskeard District, Cornwall, has been reinvestigated. The revised composition from electron microprobe analyses and structure refinement is [Al29.2Fe2.8(AsO4)18(OH)42(H2O)22]·52H2O. The crystal structure was determined using synchrotron data collected on a 2 μm diameter fibre at 100 K. Liskeardite has monoclinic symmetry, space group I2, with the unit-cell parameters a = 24.576(5), b = 7.754(2) Å, c = 24.641(5) Å, and β = 90.19(1)º. The structure was refined to R = 0.059 for 9769 reflections with I > 3σ(I). It is of an open framework type in which intersecting polyhedral slabs parallel to (101) and (10) form 17.4 Å × 17.4 Å channels along [010], with water molecules occupying the channels. Small amounts (<1 wt.%) of Na, K and Cu are probably adsorbed at the channel walls The framework comprises columns of pharmacoalumite-type, intergrown with chiral chains of six cis edge-shared octahedra. It can be described in terms of cubic close packing, with vacancies at both the anion and cation sites. The compositional and structural relationships between liskeardite and pharmacoalumite are discussed and a possible mechanism for liskeardite formation is presented.

scholarly journals The crystal structure of Ga-rich plumbogummite from Tsumeb, Namibia

2009 ◽  
Vol 73 (5) ◽  
pp. 837-845 ◽  
Author(s):  
S. J. Mills ◽  
A. R. Kampf ◽  
M. Raudsepp ◽  
A. G. Christy
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
White Light ◽  
Type Structure ◽  
Space Group ◽  
Cell Parameters ◽  
Composite Layers ◽  
Symmetry Space ◽  
Symmetry Space Group ◽  
Rhombohedral Symmetry

AbstractGa-rich plumbogummite, (Pb0.87,Ca0.13)Σ1.00H(Al1.95,Ga1.05)Σ3.00(PO4)2(OH)6, from Tsumeb, Namibia, has rhombohedral symmetry, space group Rm, with the cell parameters a = 7.0752(19) Å, c = 16.818(4) Å and V = 729.1(3) Å3. The crystal structure has been refined to R1 = 2.05%. Ga-rich plumbogummite has an alunite-type structure comprised of a rhombohedral stacking of (001) composite layers of corner-shared (Al,Ga)O6 octahedra and PO4 tetrahedra, with Pb atoms occupying icosahedrally coordinated sites between the layers. The Pb and H positions are discussed. Ga-rich plumbogummite is nonpleochroic, uniaxial (+), with indices of refraction, ε = 1.742(3) and ω = 1.722(3), determined in white light. The five strongest powder-diffraction lines [d in Å, (I/I°), (hkl)] are: 2.995, (100), (113); 5.766, (95), (101); 2.236, (43), (107, 122); 3.539, (38), (110); 1.919 (32), (303, 033).

scholarly journals Photoconductivity of the Single Crystals Pb4Ga4GeS12 and Pb4Ga4GeSe12

Proceedings ◽  
2020 ◽  
Vol 62 (1) ◽  
pp. 4
Author(s):  
Hadj Bellagra ◽  
Oksana Nyhmatullina ◽  
Yuri Kogut ◽  
Halyna Myronchuk ◽  
Lyudmyla Piskach
Keyword(s):  
Ternary Systems ◽  
Semiconductor Materials ◽  
Tetragonal Symmetry ◽  
Bandgap Energy ◽  
Experimental Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vertical Bridgman ◽  
Symmetry Space ◽  
Symmetry Space Group

Quaternary semiconductor materials of the Pb4Ga4GeS(Se)12 composition have attracted the attention of researchers due to their possible use as active elements of optoelectronics and nonlinear optics. The Pb4Ga4GeS(Se)12 phases belong to the solid solution ranges of the Pb3Ga2GeS(Se)8 compounds which form in the quasi-ternary systems PbS(Se)−Ga2S(Se)3−GeS(Se)2 at the cross of the PbGa2S(Se)4−Pb2GeS(Se)4 and PbS(Se)−PbGa2GeS(Se)6 sections. The quaternary sulfide melts congruently at 943 K. The crystallization of the Pb4Ga4GeSe12 phase is associated with the ternary peritectic process Lp + PbSe ↔ PbGa2S4 + Pb3Ga2GeSe8 at 868 K. For the single crystal studies, Pb4Ga4GeS(Se)12 were pre-synthesized by co-melting high-purity elements. The X-ray diffraction results confirm that these compounds possess non-centrosymmetric crystal structure (tetragonal symmetry, space group P–421c). The crystals were grown by the vertical Bridgman method in a two-zone furnace. The starting composition was stoichiometric for Pb4Ga4GeS12, and the solution-melt method was used for the selenide Pb4Ga4GeSe12. The obtained value of the bandgap energy for the Pb4Ga4GeS12 and Pb4Ga4GeSe12 crystals is 1.86 and 2.28 eV, respectively. Experimental measurements of the spectral distribution of photoconductivity for the Pb4Ga4GeS12 and Pb4Ga4GeSe12 crystals exhibit the presence of two spectral maxima. The first lies in the region of 570 (2.17 eV) and 680 nm (1.82 eV), respectively, and matches the optical bandgap estimates well. The locations of the admixture maxima at about 1030 (1.20 eV) and 1340 nm (0.92 eV), respectively, agree satisfactorily with the calculated energy positions of the defects vs. and VSe.

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