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.

Refinement of the layered titanosilicate AM-1 from single-crystal X-ray diffraction data

2007 ◽  
Vol 63 (11) ◽  
pp. i186-i186 ◽  
Author(s):  
Stanislav Ferdov ◽  
Uwe Kolitsch ◽  
Christian Lengauer ◽  
Ekkehart Tillmanns ◽  
Zhi Lin ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Hydrogen Bonding ◽  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Time ◽  
Ir And Raman ◽  
Bonding Scheme

The structure of the layered noncentrosymmetric titanosilicate AM-1 (also known as JDF-L1, disodium titanium tetrasilicate dihydrate), Na4Ti2Si8O22·4H2O, grown as small single crystals without the use of organics, has been refined from single-crystal X-ray diffraction data. The H atom has been located for the first time, and the hydrogen-bonding scheme is also characterized by IR and Raman spectroscopy. All atoms are in general positions except for the Na, the Ti, one Ti-bound O, one Si-bound O and the water O atoms (site symmetries 2, 4, 4, 2 and 2, respectively).

scholarly journals The crystal structure of cyanotrichite

2015 ◽  
Vol 79 (2) ◽  
pp. 321-335 ◽  
Author(s):  
Stuart J. Mills ◽  
Andrew G. Christy ◽  
Fernando Colombo ◽  
Jason R. Price
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Local Structure ◽  
Unit Cell ◽  
Group Symmetry ◽  
Hydrogen Atoms ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Cell Parameters ◽  
Bonding Scheme

AbstractWe report the single-crystal average structure of cyanotrichite, Cu4Al2[SO4](OH)12(H2O)2, from the Maid of Sunshine mine, Arizona, USA. Cyanotrichite crystallizes in space group C2/m, with the unit-cell parameters a = 12.625(3), b = 2.8950(6), c = 10.153(2) Å and β = 92.17(3)o. All non-hydrogen atoms were located and refined to R1 = 0.0394 for all 584 observed reflections [Fo > 4σFo] and 0.0424 for all 622 unique reflections. The cyanotrichite structure consists of a principal building unit of a three-wide [Cu2Al(OH)6] ribbon of edge-sharing Cu and Al polyhedra || b, similar to that found for camerolaite. The ribbons lie in layers || (001) and between these layers, while SO4 tetrahedra and H2O molecules form rods running || b. A hydrogen-bonding scheme is also proposed.A sample of cyanotrichite from the Cap Garonne mine, Le Pradet, France, showed a 4b superstructure with the following unit cell: space group P2/m, a = 12.611(2) Å, b = 11.584(16) = 4 × 2.896(4) Å, c = 10.190(1) Å and β = 92.29(6)o. The supercell could not be refined in detail, but nevertheless imposes constraints on the local structure in that while the space-group symmetry prevents full order of SO4 and H2O in the 4b supercell, it requires that the sequence of species along any given rod is [-SO4-SO4-(H2O)2-(H2O)2-] rather than [-SO4-(H2O)2-SO4-(H2O)2-].

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.

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.

X-ray Structure Refinement and Vibrational Spectroscopy of Ca8Gd2 (PO4)6 O2

2013 ◽  
Vol 12 (10) ◽  
pp. 719-726
Author(s):  
R. Ayadi ◽  
Mohamed Boujelbene ◽  
T. Mhiri
Keyword(s):  
Solid State ◽  
General Formula ◽  
Vibrational Spectroscopy ◽  
Powder Diffraction ◽  
Infrared Spectra ◽  
Solid State Reaction ◽  
Structure Refinement ◽  
Unit Cell ◽  
Cell Group ◽  
X Ray

The present paper is interested in the study of compounds from the apatite family with the general formula Ca10 (PO4)6A2. It particularly brings to light the exploitation of the distinctive stereochemistries of two Ca positions in apatite. In fact, Gd-Bearing oxyapatiteCa8 Gd2 (PO4)6O2 has been synthesized by solid state reaction and characterized by X-ray powder diffraction. The site occupancies of substituents is0.3333 in Gd and 0.3333 for Ca in the Ca(1) position and 0. 5 for Gd in the Ca (2) position.  Besides, the observed frequencies in the Raman and infrared spectra were explained and discussed on the basis of unit-cell group analyses.

Interaction of Gold Atom with Clusters of Water: Few Computational Mise-En-Scènes with Hydrogen Bonding Motif

2008 ◽  
Vol 73 (11) ◽  
pp. 1457-1474 ◽  
Author(s):  
Eugene S. Kryachko
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Computational Model ◽  
Photoelectron Spectroscopy ◽  
Water Clusters ◽  
Gold Atom ◽  
Proton Acceptor ◽  
Anion Photoelectron Spectroscopy ◽  
Relationship Of ◽  
First Time

The present work outlines the fair relationship of the computational model with the experiments on anion photoelectron spectroscopy for the gold-water complexes [Au(H2O)1≤n≤2]- that is established between the auride anion Au- and water monomer and dimer thanks to the nonconventional hydrogen bond where Au- casts as the nonconventional proton acceptor. This work also extends the computational model to the larger complexes [Au(H2O)3≤n≤5]- where gold considerably thwarts the shape of water clusters and even particularly breaks their conventional hydrogen bonding patterns. The fascinating phenomenon of the lavish proton acceptor character of Au- to form at least six hydrogen bonds with molecules of water is computationally unveiled in the present work for the first time.

scholarly journals Allanite at high temperature: effect of REE on the thermal behaviour of epidote-group minerals

2021 ◽  
Vol 48 (9) ◽  
Author(s):  
G. Diego Gatta ◽  
Francesco Pagliaro ◽  
Paolo Lotti ◽  
Alessandro Guastoni ◽  
Laura Cañadillas-Delgado ◽  
...  
Keyword(s):  
Cell Volume ◽  
Thermal Behaviour ◽  
Unit Cell Volume ◽  
Unit Cell ◽  
Atomic Scale ◽  
Elastic Behaviour ◽  
Positive Trend ◽  
Cell Parameters ◽  
Thermal Anisotropy ◽  
Different Temperatures

AbstractThe thermal behaviour of a natural allanite-(Ce) has been investigated up to 1073 K (at room pressure) by means of in situ synchrotron powder X-ray diffraction and single-crystal neutron diffraction. Allanite preserves its crystallinity up to 1073 K. However, up to 700 K, the thermal behaviour along the three principal crystallographic axes, of the monoclinic β angle and of the unit-cell volume follow monotonically increasing trends, which are almost linear. At T > 700–800 K, a drastic change takes place: an inversion of the trend is observed along the a and b axes (more pronounced along b) and for the monoclinic β angle; in contrast, an anomalous increase of the expansion is observed along the c axis, which controls the positive trend experienced by the unit-cell volume at T > 700–800 K. Data collected back to room T, after the HT experiments, show unit-cell parameters significantly different with respect to those previously measured at 293 K: allanite responds with an ideal elastic behaviour up to 700 K, and at T > 700–800 K its behaviour deviates from the elasticity field. The thermo-elastic behaviour up to 700 K was modelled with a modified Holland–Powell EoS; for the unit-cell volume, we obtained the following parameters: VT0 = 467.33(6) Å3 and αT0(V) = 2.8(3) × 10–5 K−1. The thermal anisotropy, derived on the basis of the axial expansion along the three main crystallographic directions, is the following: αT0(a):αT0(b):αT0(c) = 1.08:1:1.36. The T-induced mechanisms, at the atomic scale, are described on the basis of the neutron structure refinements at different temperatures. Evidence of dehydroxylation effect at T ≥ 848 K are reported. A comparison between the thermal behaviour of allanite, epidote and clinozoisite is carried out.

scholarly journals Study of Structural, Magnetic, and Mossbauer Properties of Dy2Fe16Ga1−xNbx (0.0 ≤ x ≤ 1.0) Prepared via Arc Melting Process

2021 ◽  
Vol 7 (3) ◽  
pp. 42
Author(s):  
Jiba N. Dahal ◽  
Kalangala Sikkanther Syed Ali ◽  
Sanjay R. Mishra
Keyword(s):  
Isomer Shift ◽  
Cell Volume ◽  
Intermetallic Compounds ◽  
Unit Cell Volume ◽  
Rietveld Analysis ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Arc Melting ◽  
Nb Content

Intermetallic compounds of Dy2Fe16Ga1−xNbx (x = 0.0 to 1.00) were synthesized by arc melting. Samples were investigated for structural, magnetic, and hyperfine properties using X-ray diffraction, vibration sample magnetometer, and Mossbauer spectrometer, respectively. The Rietveld analysis of room temperature X-ray diffraction data shows that all the samples were crystallized in Th2Fe17 structure. The unit cell volume of alloys increased linearly with an increase in Nb content. The maximum Curie temperature Tc ~523 K for x = 0.6 sample is higher than Tc = 153 K of Dy2Fe17. The saturation magnetization decreased linearly with increasing Nb content from 61.57 emu/g for x = 0.0 to 42.46 emu/g for x = 1.0. The Mössbauer spectra and Rietveld analysis showed a small amount of DyFe3 and NbFe2 secondary phases at x = 1.0. The hyperfine field of Dy2Fe16Ga1−xNbx decreased while the isomer shift values increased with the Nb content. The observed increase in isomer shift may have resulted from the decrease in s electron density due to the unit cell volume expansion. The substantial increase in Tc of thus prepared intermetallic compounds is expected to have implications in magnets used for high-temperature applications.

scholarly journals Crystal Structure Refinements of Four Monazite Samples from Different Localities

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1028 ◽  
Author(s):  
M. Mashrur Zaman ◽  
Sytle M. Antao
Keyword(s):  
Crystal Structure ◽  
Electron Probe ◽  
Unit Cell Volume ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Large Unit Cell ◽  
A Site

This study investigates the crystal chemistry of monazite (APO4, where A = Lanthanides = Ln, as well as Y, Th, U, Ca, and Pb) based on four samples from different localities using single-crystal X-ray diffraction and electron-probe microanalysis. The crystal structure of all four samples are well refined, as indicated by their refinement statistics. Relatively large unit-cell parameters (a = 6.7640(5), b = 6.9850(4), c = 6.4500(3) Å, β = 103.584(2)°, and V = 296.22(3) Å3) are obtained for a detrital monazite-Ce from Cox’s Bazar, Bangladesh. Sm-rich monazite from Gunnison County, Colorado, USA, has smaller unit-cell parameters (a = 6.7010(4), b = 6.9080(4), c = 6.4300(4) Å, β = 103.817(3)°, and V = 289.04(3) Å3). The a, b, and c unit-cell parameters vary linearly with the unit-cell volume, V. The change in the a parameter is large (0.2 Å) and is related to the type of cations occupying the A site. The average <A-O> distances vary linearly with V, whereas the average <P-O> distances are nearly constant because the PO4 group is a rigid tetrahedron.

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