Structural and chemical study of weishanite, (Au,Ag,Hg), from the Keystone mine, Colorado, USA.

2018 ◽  
Vol 82 (5) ◽  
pp. 1141-1145
Author(s):  
Luca Bindi ◽  
Frank N. Keutsch ◽  
Giovanni O. Lepore
Keyword(s):  
Electron Microprobe ◽  
Structural Data ◽  
Chemical Study ◽  
Critical Discussion ◽  
Unit Cell ◽  
Structural Position ◽  
Space Group ◽  
Microprobe Data ◽  
First Time

ABSTRACTStructural data for weishanite, an alloy of Au, Ag and Hg, were collected for the first time from a crystal from the Keystone Mine, Colorado, USA. The structure was solved in the space group P63/mmc with the unit cell a = 2.9348(8) and c = 4.8215(18) Å] and refined to R = 0.0299 for 40 observed reflections [4σ(F) level] and four parameters and to R = 0.0356 for all 47 independent reflections. The weishanite structure can be considered a derivative of the zinc structure, with Au, Ag and Hg disordered in the same structural position. On this basis, we suggest that the formula is normalized to 1 atom with Z = 2, leading, for the sample investigated, to Au0.41Ag0.31Hg0.28 (electron microprobe data). Accordingly, weishanite can be considered the Au-rich isotype of schachnerite. A comparison with other Au/Ag-Hg alloys is presented together with a critical discussion about the nomenclature rules to be applied to alloys and simple metals.

Michael addition of phenylacetonitrile to the acrylonitrile group leading to diphenylpentanedinitrile. Structural data and theoretical calculations

2014 ◽  
Vol 68 (5) ◽  
Author(s):  
M. Percino ◽  
Margarita Cerón ◽  
Maria Castro ◽  
Guillermo Soriano-Moro ◽  
Victor Chapela ◽  
...  
Keyword(s):  
Michael Addition ◽  
Theoretical Calculations ◽  
Structural Data ◽  
Unit Cell ◽  
Structure Property ◽  
Unit Cell Parameters ◽  
Monoclinic System ◽  
Space Group ◽  
Cell Parameters ◽  
Structure Property Relationships

AbstractKnoevenagel condensation of phenylacetonitrile with 4-diphenylaminophenylacetonitrile in the presence of piperidine was carried out to obtain a novel conjugated compound. In addition to the expected compound 2-(phenyl)-3-(4-diphenylaminophenyl)acrylonitrile (I), the 3-((4-diphenylamino)phenyl)-2,4-diphenylpentanedinitrile (II) was also obtained with a good yield. Compound II was obtained as a result of the Michael addition of phenylacetonitrile with 2-(phenyl)-3-(4-diphenylaminophenyl)acrylonitrile (I). Conversely, when the same reaction was performed in the presence of KOH as catalyst, only the α,β-unsaturated nitrile (I) was afforded with a 92 % yield. The structures were confirmed with IR, EI-MS and NMR spectroscopy. Single crystals I and II were formed and their structures were determined by X-ray single-crystal diffraction analysis. Crystal I belongs to the monoclinic system with space group P21/n having unit cell parameters of a = 16.8589(5) Å, b = 6.68223(17) Å, c = 19.8289(7) Å, β = 111.133(4)○ and Z = 4. Crystal II belongs to the same monoclinic system with space group P21/c, having unit cell parameters of a = 10.8597(4) Å, b = 24.7533(10) Å, c = 9.7832(4) Å, β = 91.297(3)○ and Z = 4. In addition to the structural data analysis, some theoretical calculations that reveal the nature of relevant structure-property relationships are also reported.

scholarly journals Lead-antimony sulfosalts from Tuscany (Italy). XIX. Crystal chemistry of chovanite from two new occurrences in the Apuan Alps and its 8 Å crystal structure

2017 ◽  
Vol 81 (4) ◽  
pp. 811-831 ◽  
Author(s):  
Cristian Biagioni ◽  
Yves Moëlo
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Crystal Chemistry ◽  
Electron Microprobe ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Cell Parameters ◽  
New Occurrences ◽  
Apuan Alps

AbstractTwo new occurrences of the lead oxy-sulfosalt chovanite have been identified at the Monte Arsiccio and Pollone mines, Apuan Alps, Tuscany, Italy. Chovanite from Monte Arsiccio occurs as black acicular crystals, up to 5 mm long, associated with rouxelite, robinsonite, sphalerite, valentinite,baryte, dolomite, quartz and Ba-rich K-feldspar ('hyalophane') in metadolostone vugs. Its unit-cell parameters are a = 48.38(5), b = 4.11(4), c = 34.18(4) Å, β = 106.26(2)°, V = 6521(64) Å3, space group C2/m. Very weakreflections indicate the doubling of the b parameter. Electron-microprobe data gave (wt.%): Ag 0.28, Tl 1.51, Pb 45.57, Sb 31.00, As 1.09, S 19.73, Se 0.05, Cl 0.02, sum 99.25. On the basis of ∑Me = 58 apfu, its formula is Ag0.30Tl0.86Pb25.56Sb29.59As1.69S71.52Se0.07Cl0.05.Adding one oxygen atom, it is close to the formula TlPb26(Sb,As)31S72O. Chovanite from Pollone occurs as thick black acicular crystals, up to 1 cm long, associated with baryte and quartz. The high-diffraction quality of the available material allowed the solutionand refinement of the 8 Å crystal structure in the space group P21/c, with unit-cell parameters a = 34.052(3), b = 8.2027(7), c = 48.078(4) Å, β = 106.258(4)°, V = 12891.9(19) Å3. The refinement convergedto R1 = 9.14% on the basis of 19,853 observed reflections with Fo > 4σ(Fo). Electron-microprobe data gave (wt.%): Ag 0.12, Tl 0.54, Pb 48.34, Bi 0.20, Sb 26.71, As 3.37, S 20.23, Cl 0.07, sum 99.57. It corresponds to the formulaAg0.13Tl0.30Pb26.94Bi0.10Sb25.33As5.20S72.85Cl0.20, close to the idealized formula Pb28(Sb,As)30S72O, with a single oxygen atom bound to two (Sb/As) atoms alternating witha vacancy along b as in scainiite and in other Pb oxy-sulfosalts. The crystal chemistry of this 8 Å crystal structure is detailed, taking into account its modular description, the (Sb,As)mSn polymerization, its topological derivation from pellouxite,and the oxygen non-stoichiometry.

Armstrongite from the Strange Lake Alkalic Complex, on the Quebec – Labrador Boundary, Canada

1987 ◽  
Vol 2 (1) ◽  
pp. 2-4 ◽  
Author(s):  
John L. Jambor ◽  
Andrew C. Roberts ◽  
Joel D. Grice
Keyword(s):  
Electron Microprobe ◽  
Unit Cell ◽  
Powder Pattern ◽  
Theoretical Formula ◽  
Monoclinic Space Group ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
No Absorption

AbstractTabular untwinned crystals of colorless transparent armstrongite from the Strange Lake Alkalic Complex, on the Quebec – Labrador boundary, Canada are monoclinic, space group choices I2/m, I2, Im (diffraction aspect I*/*), with refined unit-cell parameters a = 13.599 (9), b = 14.114(9), c = 7.833 (4) Å, β = 103.41 (5)°, V = 1462.4 (±3.0) Å3. a:b:c = 0.9635:1:0.5550, Z = 4 and D(x) = 2.696 g/cm3. A fully indexed X-ray powder pattern is presented. Averaged electron-microprobe analyses suggest a theoretical formula of CaZrSi6O15 · 3 H2O. The Strange Lake armstrongite is biaxial negative, α = 1.567 (1), β = 1.576 (1), γ = 1.577 (1), 2V (meas.) = 39 (1)°, 2V (calc.) = 37°, Z∥b, X Λc = +4°, with no absorption and weak dispersion r < v.

The surprisingly elusive crystal structure of sodium metabisulfite

2004 ◽  
Vol 60 (2) ◽  
pp. 155-162 ◽  
Author(s):  
Kay L. Carter ◽  
Tasneem A. Siddiquee ◽  
Kristen L. Murphy ◽  
Dennis W. Bennett
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Low Temperature ◽  
Unit Cell ◽  
Sodium Metabisulfite ◽  
Asymmetric Unit ◽  
Space Group ◽  
Crystal Fragment ◽  
First Time ◽  
Correct Structure

The crystal structure of Na2S2O5, a simple and common ionic compound, is reported here for the first time. The crystals form non-merohedral twins, with the twin domains related by a twofold axis which bisects the angle between the a and c axes of each unit cell. The structure was determined from a single-crystal fragment of a twinned crystal that had undergone cleavage along the twin boundary. In addition to the problems associated with twinning, space-group determination proved difficult as well, with the structure initially determined in the P21 space group appearing to be disordered with two rotational conformers of the metabisulfite ion occupying equivalent sites in the lattice. An analysis at low temperature provided new weak reflections which were inconsistent with the original unit cell, but indexed to the correct unit cell, allowing for space group and crystal structure determination. The apparent structure, which appeared disordered in P21, seems to have resulted from an apparently fortuitous superposition of two conformationally inequivalent S2O_5^{2-} anions in the asymmetric unit of the correct structure in the P21/n space group. The metabisulfite ions in this structure do not adopt the Cs geometry observed in previously determined crystal structures containing S2O_5^{2-}. The structures of both ions in the asymmetric unit are effectively conformational mirror images of one another with two of the O atoms on each S atom in the ion approaching an eclipsed geometry. This observation provides further evidence that the structures of sulfur-oxy anions in the solid state are dictated mainly by interionic coulombic forces rather than by intraionic bonding interactions

scholarly journals Spektroskopische und strukturelle Aspekte der Protonierung von Tetraaza[14]annulen-Dianionen / Spectroscopic and Structural Aspects of the Protonation of Tetraaza[14]annulene Dianions

1996 ◽  
Vol 51 (9) ◽  
pp. 1255-1266 ◽  
Author(s):  
H. Schumann ◽  
B. Neumann ◽  
H.- G. Stammler
Keyword(s):  
Structural Data ◽  
X Ray Diffraction ◽  
Space Group ◽  
Crystal System ◽  
Additional Information ◽  
R Factor ◽  
Vis Spectroscopy ◽  
First Time ◽  
Structural Aspects ◽  
C Nmr

The effects of increasing protonation upon two [ 14]annulene dianions prepared by reaction of LiCH3 with 5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][l,4,8,l l]tetraazacyclotetradecine (IIIb) and 5,14-dihydro-6,17-dimethyl-8,15-diphenyldibenzo[b,i][l,4,8,l 1 ]tetraazacyclotetradecine (IIIc) have been studied by 1H, 13C NMR and UV-VIS spectroscopy in solution. The crystal structures of the diprotonated macrocycle IIIb x 2 HPF6 (lIb) and of the neutral macrocycle IIIc have been determined by X-ray diffraction. For lIb, the crystal system is monoclinic with a space group of P21/n: a = 12.019(3), b = 13.864(6), c = 33.547(9) Å, β = 99.82(2)°, Z = 8 . The final R factor is 0.083 for 5520 observed reflections (745 variables). For IIIc, the crystal system is triclinic with a space group of P1̄: a = 9.923(8), b = 11.633(9), c = 14.318(12) Å, ct = 110.50(6)°, β = 98.86(7)°, 7 = 103.12(6)°, Z = 2. The final R factor is 0.081 for 2174 observed reflections and 191 variables. Comparison of these structural data together with those obtained from the literature for the deprotonated macrocycle IVb and a wide variety of substituted [ 14]annule derivatives allows for the first time a discussion of protonation effects upon the highly π-conjugated pentadiimidato moiety. Additional information is derived from NMR and UV-VIS data.

The X-Ray Crystallography of Rosasite From Tsumeb, Namibia

1986 ◽  
Vol 1 (1) ◽  
pp. 56-57 ◽  
Author(s):  
Andrew C. Roberts ◽  
John L. Jambor ◽  
Joel D. Grice
Keyword(s):  
Electron Microprobe ◽  
Analytical Formula ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
X Ray Crystallography ◽  
Bluish Green

AbstractCrystals of green to bluish green rosasite from Tsumeb, Namibia are monoclinic, space group P21/a, with refined unit-cell parameters a = 12.873 (3), b = 9.354 (3), c = 3.156 (2) A, β = 110.36 (3)°, V = 356.3 (5) A3 and a:b:c = 1.3762:1:0.3374, with Z = 4 and Dx = 4.15 g./cm.3. Crystals are twinned by 180° rotation about a*. A fully indexed powder pattern is presented. Electron-microprobe analyses, average (wt. %): Cu 32.9, Zn 23.7; this suggests an analytical formula of (Cu1·18 Zn0·82) (CO3) (OH)2. The rosasite is optically biaxial negative, α = 1.673 (1), β = 1.796 (3), γ = 1.811 (3), 2Vx = 33 (5)° (calc. 36.4°), with X = c, Y = a* and Z = b.

scholarly journals The crystal chemistry of elsmoreite from the Hemerdon (Drakelands) mine, UK: hydrokenoelsmoreite-3C and hydrokenoelsmoreite-6R

2016 ◽  
Vol 80 (7) ◽  
pp. 1195-1203 ◽  
Author(s):  
Stuart J. Mills ◽  
Andrew G. Christy ◽  
Mike S. Rumsey ◽  
John Spratt
Keyword(s):  
United Kingdom ◽  
Cell Parameter ◽  
Chemical Study ◽  
Unit Cell ◽  
Chemical Analyses ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Cell Parameters ◽  
Al Substitution ◽  
Long Range Ordering

AbstractA crystallographic and chemical study of two 'elsmoreite' samples (previously described as 'ferritungstite') from the Hemerdon mine (now known as the Drakelands mine), Devon, United Kingdom has shown them to be two different polytypes of hydrokenoelsmoreite. Hydrokenoelsmoreite-3C(HKE-3C) crystallizes in space group , with the unit-cell parameter a = 10.3065(3) Å. Hydrokenoelsmoreite-6R (HKE-6R) crystallizes in space group , with the unit-cell parameters a = 7.2882(2) Å and c = 35.7056(14)Å. Chemical analyses showed that both polytypes have Na and Fe/Al substitution giving the formulae: (Na0.28Ca0.04K0.02(H2O)0.20⁏1.46)∑2.00(W1.47Fe3+0.32Al0.21As5+0.01)∑2.00[O4.79(OH)1.21]∑6.00·(H2O)(3C) and (Na0.24Ca0.04K0.03(H2O)0.63⁏1.06)∑2.00(W1.42Fe3+0.49Al0.08As5+0.01)∑2.00[O4.65(OH)1.35]∑6.00·(H2O)(6R). The doubling of the unit cell in the 6R phase is due to ordering of Na and ( ,H2O) in the A site; no long-range ordering is observed between W and Fe/Al in the B site.

scholarly journals Stoichiometric partially-protonated states in hydroxide perovskites: the jeanbandyite enigma revisited

2017 ◽  
Vol 81 (2) ◽  
pp. 297-303 ◽  
Author(s):  
Mark D. Welch ◽  
Anthony R. Kampf
Keyword(s):  
Structure Determination ◽  
Structure Refinement ◽  
Structural Data ◽  
Original Description ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Long Range Ordering

AbstractThe original description of the hydroxide perovskite jeanbandyite gives a formula (Fe1–x3+,□x)(Sn1–y,□y) (OH)6 (□= vacancy), which implies the possibility of stoichiometric vacancies at B and B' sites. The validity of this formula has been questioned subsequently. Furthermore, jeanbandyite has metrically a cubic unit cell, but it is optically uniaxial. It is clear that a structure determination is needed to clarify the nature of this enigmatic mineral. Previous studies could find no crystals of sufficient quality for structure determination using X-ray diffractometers available at the time. Crystals of jeanbandyite from Hingston Down, Cornwall, UK and the type locality Llallagua, Bolivia, have been found that are of a quality that allows structure refinement by single-crystal X-ray diffraction. Structural data for crystals from each locality are presented that clarify the nature of jeanbandyite and raise some interesting questions concerning the significance of partially deprotonated states in perovskite-type structures. The structures of both jeanbandyite crystals are cubic with space group Pn3 and unit-cell parameters a = 7.658(2) Å (Llallagua) and 7.6427(2) Å (Hingston). The octahedral tilt system is a+a+a+ and corresponds to that of the aristotype of BB'(OH)6 hydroxide double perovskites. Structure determination demonstrates that B is very Fe3+-rich and B' is filled by Sn, thereby requiring revision of the general jeanbandyite formula to Fex3+Fe(1–x)2+Sn(OH)(6–x)Oxfor 1≥ × > 0.5, with an ideal end-member formula Fe3+Sn(OH)5O. As such, jeanbandyite corresponds to oxidized natanite with partially deprotonated oxygen sites. This stoichiometry cannot be represented in space group Pn3̄ for the observed unit cell as it implies more than one non-equivalent oxygen atom. Consequently, it is inferred that there is no long-range ordering of deprotonated oxygen sites. It is, however, conceivable that the uniaxial optical character of jeanbandyite is linked to the local short-range order of deprotonated domains.

scholarly journals Crystal structure of the uranyl arsenate mineral hügelite, Pb2(UO2)3O2(AsO4)2(H2O)5, revisited: a correct unit cell, twinning and hydrogen bonding

2021 ◽  
Vol 77 (3) ◽  
Author(s):  
Jakub Plášil ◽  
Václav Petříček ◽  
Pavel Škácha
Keyword(s):  
Hydrogen Bonding ◽  
Unit Cell Volume ◽  
Structure Refinement ◽  
Structural Data ◽  
Unit Cell ◽  
Orthorhombic Unit Cell ◽  
Real Cell ◽  
Structure Description ◽  
First Time ◽  
Bonding Scheme

Revisiting the structure of uranyl arsenate mineral hügelite provided some corrections to the available structural data. The previous twinning model (by reticular merohedry) in hügelite has been corrected. Twinning of the monoclinic unit cell [a = 7.0189 (7) Å, b = 17.1374 (10) Å, c = 8.1310 (10) Å and β = 108.904 (10)°], which can be expressed as a mirror in [100], leads to a pseudo-orthorhombic unit cell (a = 7.019 Å, b = 17.137 Å, c = 61.539 Å and β = 90.02°), which is eight times larger, with respect to the unit-cell volume, than a real cell. Moreover, the unit cell of chosen here and the unit cell given by the previous structure description both lead to the same supercell. A new structure refinement undertaken on an untwinned crystal of hügelite resulted in R = 4.82% for 12 864 reflections with I obs > 3σ(I) and GOF = 1.12. The hydrogen-bonding scheme has been proposed for hügelite for the first time.

Bence-albee after 25 years: A new superior α-factor correction procedure for the quantitative analysis of oxides and silicates

1992 ◽  
Vol 50 (2) ◽  
pp. 1744-1745
Author(s):  
John T. Armstrong
Keyword(s):  
Quantitative Analysis ◽  
Electron Microprobe ◽  
Binary Systems ◽  
Correction Procedure ◽  
Geological Samples ◽  
The Past ◽  
Large Matrix ◽  
Computational Speed ◽  
Microprobe Data ◽  
Geological Sciences

One of the most cited papers in the geological sciences has been that of Albee and Bence on the use of empirical " α -factors" to correct quantitative electron microprobe data. During the past 25 years this method has remained the most commonly used correction for geological samples, despite the facts that few investigators have actually determined empirical α-factors, but instead employ tables of calculated α-factors using one of the conventional "ZAF" correction programs; a number of investigators have shown that the assumption that an α-factor is constant in binary systems where there are large matrix corrections is incorrect (e.g, 2-3); and the procedure’s desirability in terms of program size and computational speed is much less important today because of developments in computing capabilities. The question thus exists whether it is time to honorably retire the Bence-Albee procedure and turn to more modern, robust correction methods. This paper proposes that, although it is perhaps time to retire the original Bence-Albee procedure, it should be replaced by a similar method based on compositiondependent polynomial α-factor expressions.

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