scholarly journals Crystal structure determination of karibibite, an Fe3+ arsenite, using electron diffraction tomography

2017 ◽  
Vol 81 (5) ◽  
pp. 1191-1202 ◽  
Author(s):  
Fernando Colombo ◽  
Enrico Mugnaioli ◽  
Oriol Vallcorba ◽  
Alberto García ◽  
Alejandro R. Goñi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Dft Calculations ◽  
Density Functional ◽  
Weak Interactions ◽  
Diffraction Tomography ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Parameters

AbstractThe crystal structure of karibibite, Fe33+(As3+O2)4(As23+O5)(OH), from the Urucum mine (Minas Gerais, Brazil), was solved and refined from electron diffraction tomography data [R1 = 18.8% for F > 4σ(F)] and further confirmed by synchrotron X-ray diffraction and density functional theory (DFT) calculations. The mineral is orthorhombic, space group Pnma and unit-cell parameters (synchrotron X-ray diffraction) are a = 7.2558(3), b = 27.992(1), c = 6.5243 (3) Å, V = 1325.10(8) Å3, Z = 4. The crystal structure of karibibbite consists of bands of Fe3+O6 octahedra running along a framed by two chains of AsO3 trigonal pyramids at each side, and along c by As2O5 dimers above and below. Each band is composed of ribbons of three edge-sharing Fe3+O6 octahedra, apex-connected with other ribbons in order to form a kinked band running along a. The atoms As(2) and As(3), each showing trigonal pyramidal coordination by O, share the O(4) atom to form a dimer. In turn, dimers are connected by the O(3) atoms, defining a zig-zag chain of overall (As3+O2)n-n stoichiometry. Each ribbon of (Fe3+O6) octahedra is flanked on both edges by the (As3+O2)n-n chains. The simultaneous presence of arsenite chains and dimers is previously unknown in compounds with As3+. The lone-electron pairs (4s2) of the As(2) and As(3) atoms project into the interlayer located at y = 0 and y = ½, yielding probable weak interactions with the O atoms of the facing (AsO2) chain.The DFT calculations show that the Fe atoms have maximum spin polarization, consistent with the Fe3+ state.

Determination of the Crystal Structure and Redefinition of Tsugaruite, Pb28As15S50Cl, the First Lead-Arsenic Chloro-Sulfosalt

2020 ◽  
Author(s):  
Cristian Biagioni ◽  
Luca Bindi ◽  
Koichi Momma ◽  
Ritsuro Miyawaki ◽  
Yoshitaka Matsushita ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Atomic Ratio ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Specific Position ◽  
Actual Classification ◽  
Aomori Prefecture

Abstract Tsugaruite was originally defined as a lead-arsenic sulfosalt from the Yunosawa mine, Aomori Prefecture, Japan. Until recently its crystal structure remained unsolved and its actual classification in the sulfosalt realm was unknown. Here the refinement of the crystal structure of tsugaruite using single-crystal X-ray diffraction data is reported. The mineral is orthorhombic, space group P2nn, with unit-cell parameters a = 8.0774(10), b = 15.1772(16), c = 38.129(4) Å, V = 4674.3(9) Å3, in agreement with previous studies. The solution of the crystal structure of this mineral revealed Cl occupying a specific position. Chlorine was thus sought and found using the electron microprobe; the average of six spot analyses gave (in wt.%): Pb 68.04, As 12.83, S 18.29, Cl 0.63, total 99.80. The empirical formula, calculated on the basis of Pb + As = 43 atoms per formula unit, is Pb28.26As14.74S49.08Cl1.52. Tsugaruite is an N = 4 plesiotypic derivative of the homologous series of Pb-Sb chloro-sulfosalts having the general formula Pb(2+2N)(Sb,Pb)(2+2N)S(2+2N)(S,Cl)(4+2N)ClN. It has a Cl/(Cl + S) atomic ratio close to that of other known Pb-Sb chloro-sulfosalts (pillaite, pellouxite) and slightly higher than that of dadsonite.

scholarly journals Crystal structure of vyacheslavite, U(PO4)(OH), solved from natural nanocrystal: a precession electron diffraction tomography (PEDT) study and DFT calculations

RSC Advances ◽  
2019 ◽  
Vol 9 (34) ◽  
pp. 19657-19661 ◽  
Author(s):  
Gwladys Steciuk ◽  
Seyedayat Ghazisaeed ◽  
Boris Kiefer ◽  
Jakub Plášil
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Electron Diffraction ◽  
Dft Calculations ◽  
Density Functional ◽  
Diffraction Tomography ◽  
Functional Theory ◽  
Phosphate Mineral ◽  
Precession Electron Diffraction ◽  
Nano Crystal

The crystal structure of the U(iv)-phosphate mineral vyacheslavite has been solved from precession electron diffraction tomography (PEDT) data from the natural nano-crystal and further refined using density-functional theory (DFT) calculations.

scholarly journals The crystal structure of parkinsonite, nominally Pb7MoO9Cl2: a naturally occurring Aurivillius phase

2010 ◽  
Vol 74 (2) ◽  
pp. 269-275 ◽  
Author(s):  
G. O. Lepore ◽  
M. D. Welch
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
X Ray Diffraction ◽  
Aurivillius Phase ◽  
X Ray ◽  
Cell Parameters ◽  
Naturally Occurring ◽  
Final Agreement ◽  
Fourfold Axis ◽  
Synthetic Crystal

AbstractThe crystal structure of the sheet oxychloride mineral parkinsonite, nominally Pb7MoO9Cl2, has been determined for synthetic and natural crystals of analysed compositions, (Pb7.28Mo0.72) O8.96Cl1.96 and (Pb7.23Mo0.40V0.37)O8.90Cl1.82, respectively. Parkinsonite is tetragonal, space group I4/mmm. Unit-cell parameters for synthetic and natural crystals are: asynthetic = 3.9773(4) Å, csynthetic = 22.718(4) Å, Vsynthetic = 359.38(5) Å3, and anatural = 3.9570(3) Å, cnatural = 22.634(5) Å, Vnatural = 354.40(5) Å3. Final agreement indices (R1, wR2) for refinements of the two crystals are 0.024, 0.067 (synthetic) and 0.036, 0.078 (natural). Although a superlattice has been identified by electron diffraction for crystals of both samples (Welch et al., 1996), only the substructure could be determined by X-ray diffraction. This X-ray invisibility of the superstructure has also been observed for the closely related sheet oxychlorides asisite and schwartzembergite, for both of which superstructure motifs have been identified by electron diffraction. The Pb(1) site of both parkinsonite crystals is fully occupied by Pb. Refinement of the Pb content of the Pb(2) site for the synthetic and natural crystals gives occupancies of 0.85(1) and 0.70(1) respectively, corresponding to 3.40 and 2.80 Pb(2) a.p.f.u. respectively. The substituent cation Mo (synthetic crystal) and [Mo+V] (natural crystal) was located at a distance of 0.5 Å from Pb(2), being displaced along the fourfold axis. The reduced occupancy of Pb(2) is due to substitution by Mo or [Mo+V]. No evidence for separate Mo and V sites in the substructure of natural parkinsonite was found. Refined occupancies of the Cl site are 0.84(4) and 0.91(5) for the synthetic and natural crystals, respectively, and are consistent with the 9:1 superstructure component identified by electron diffraction.

scholarly journals Vibrational Study, Reinvestigation of the Crystal Structure of MgHPO4.3H2O and Calculated IR Frequencies for the PO43- by Isotopic Substitutions

2021 ◽  
Vol 12 (3) ◽  
pp. 4140-4154
Keyword(s):  
Crystal Structure ◽  
Group Analysis ◽  
Factor Group ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Vibrational Study ◽  
Ir Frequencies

The monohydrogenomonophosphatetrihydrate of magnesium MgHPO4.3H2O was reinvestigated by X-ray diffraction, vibrational spectroscopy, nuclear magnetic resonance and calculation of the IR frequencies by using isotopic substitutions. MgHPO4.3H2O is orthorhombic, space group Pbca with the following unit-cell parameters: a = 10.0133(2) Å, b= 10.2136(1) Å, c =10.6853(2) Å, Z = 8 and V = 1092.81(3) Å3. Raman and infrared spectra of MgHPO4.3H2O have been recorded and interpreted on the basis of factor group analysis. The occurrence of the four frequencies ν1, v2, v3, v4 in the vibrational spectra confirms the existence of the PO43− tetrahedron.

Single-Crystal Structures and Vibrational Spectra of Li[SCN] and Li[SCN] · 2H2O

2014 ◽  
Vol 69 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Olaf Reckeweg ◽  
Armin Schulz ◽  
Björn Blaschkowski ◽  
Thomas Schleid ◽  
Francis J. DiSalvo
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Vibrational Spectra ◽  
Water Molecules ◽  
Infrared And Raman Spectra ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Single Crystal Structures

The crystal structure of Li[SCN] · 2 H2O has been determined by single-crystal X-ray diffraction on commercially available material. Crystals of this compound are colorless, transparent and hygroscopic. Li[SCN] · 2H2O adopts the orthorhombic space group Pnma with the cell parameters a = 572.1(3), b = 809.3(4) and c = 966.9(4) pm and Z = 4. Li[SCN] was obtained by dehydration of the afore-mentioned dihydrate and also crystallizes orthorhombically in Pnma with the lattice parameters a = 1215.1(3), b = 373.6(1) and c = 529:9(2) pm (Z = 4). Both compounds contain Li+ cations in sixfold coordination. Four water molecules and two nitrogen-attached thiocyanate anions [SCN]- arrange as trans-octahedra [Li(OH2)4(NCS)2]- in the case of Li[SCN] · 2 H2O. Anhydrous Li[SCN] displays fac-octahedra [Li(NCS)3(SCN)3]5- with six thiocyanate anions grafting via both nitrogen and sulfur atoms, three each. Infrared and Raman spectra of both compounds were recorded and a DSC=TG measurement was performed on Li[SCN] · 2 H2O.

Pressure-induced polymorphism in nanostructured SnSe

2016 ◽  
Vol 49 (1) ◽  
pp. 213-221 ◽  
Author(s):  
Sergio Michielon de Souza ◽  
Hidembergue Ordozgoith da Frota ◽  
Daniela Menegon Trichês ◽  
Angsula Ghosh ◽  
Puspitapallab Chaudhuri ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Rietveld Method ◽  
X Ray Diffraction ◽  
Synchrotron Source ◽  
X Ray ◽  
Cell Parameters ◽  
Theoretical Approaches ◽  
Diffraction Patterns ◽  
Murnaghan Equation

The pressure-induced phase transitions in nanostructured SnSe were investigated using angle-dispersive X-ray diffraction in a synchrotron source along with first-principles density functional theory (DFT) calculations. The variation of the cell parameters along with enthalpy calculations for pressures up to 18 GPa have been considered. Both the experimental and the theoretical approaches demonstrate a phase transition at around 4 GPa. Below 8.2 GPa the X-ray diffraction patterns were fitted using the Rietveld method with space groupPnma(No. 62). The lattice parameters and atomic positions for the above-mentioned symmetry were used in DFT calculations of thermodynamic parameters. The enthalpy calculations with the computationally optimized structure and the proposedPnmastructure of SnSe were compatible. The variations of the cell volume for the high-pressure phases are described by a third-order Birch–Murnaghan equation of state.

scholarly journals Synthesis, Characterization, and X-Ray Crystal Structure of Bis(O-amyl dithiocarbonato-κ2S,S′)bis(4-cyanopyridine-κN)nickel(II)

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Kuldeep Singh ◽  
Sanjay Kapoor ◽  
Renu Sachar ◽  
Vivek K. Gupta ◽  
Rajni Kant
Keyword(s):  
Crystal Structure ◽  
Magnetic Moment ◽  
Direct Methods ◽  
Title Complex ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Orthorhombic Space Group ◽  
Full Matrix ◽  
X Ray ◽  
Cell Parameters

The [Ni(S2CO-n-C5H11)2(C6H4N2)2] adduct of 4-cyanopyridine with [Ni(S2CO-n-C5H11)2] was synthesized and characterized by elemental analysis, magnetic susceptibility measurement, IR, electronic spectral data, and X-ray diffraction analysis. The Ni atom in the title complex is octahedrally coordinated within a trans-N2S4 donor set, with the Ni atom located on a centre of inversion. The title compound exhibits magnetic moment value (3.20 B.M) which is in agreement with magnetic moment values observed for paramagnetic octahedral complexes of nickel(II). The title complex crystallizes in the orthorhombic space group Pbca with unit cell parameters a = 11.455(5), b = 9.602(4), and c = 26.374(1) Å. Crystal structure was solved by direct methods and refined by full matrix least-squares procedures to a final R value of 0.0499 for 2004 observed reflections. The amyl chain is disordered over two sets of sites, with occupancy ratios of 0.595 : 0.405. Infinite long chains of molecules are formed with the help of C–H⋯N hydrogen bond.

The first pseudo-ternary thiocyanate containing two alkali metals – synthesis and single-crystal structure of LiK2[SCN]3

2016 ◽  
Vol 71 (2) ◽  
pp. 161-164 ◽  
Author(s):  
Olaf Reckeweg ◽  
Francis J. DiSalvo
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Alkali Metals ◽  
Single Crystal Structure ◽  
Rectangular Plates ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

AbstractA procedure was empirically developed to prepare the compound LiK2[SCN]3, which forms colorless, transparent, very fragile, and extremely hygroscopic thin rectangular plates. Its unique crystal structure was determined by single-crystal X-ray diffraction. LiK2[SCN]3 adopts the orthorhombic space group Pna21 (no. 33, Z = 4) with the cell parameters a = 1209.32(9), b = 950.85(9), and c = 849.95(6) pm.

Synthesis, Spectral and Thermal Properties, and Crystal Structure of Bis(ethylenediamine)(aqua)copper(II) (Bis)syringate Ethylenediamine Dihydrate [Cu(en)2(H2O)](sy)2(en)(H2O)2

2006 ◽  
Vol 61 (3) ◽  
pp. 287-291 ◽  
Author(s):  
Zerrin Heren ◽  
Hümeyra Pa§aoğlu ◽  
Gökhan Ka§tas ◽  
Leyla Vurucu ◽  
Orhan Büyükgüngör
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Thermal Properties ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Orthorhombic Space Group ◽  
Apical Position ◽  
X Ray ◽  
Cell Parameters ◽  
Electronic And Vibrational Spectra

Abstract The complex [Cu(en)2(H2O)](sy)2(en)(H2O)2 has been synthesized and characterized by its electronic and vibrational spectra. The molecular structure of the complex has been determined by X-ray diffraction methods. The complex crystallizes in the orthorhombic space group Pnma with unit-cell parameters a =10.7236(5), b= 20.4660(10), c= 14.4523(11) Å and Z=4. In the cation, the Cu(II) ion has a distorted square pyramidal coordination with two bidendate (en) ligands forming the basal plane and a H2O molecule in the apical position. The complex cations and syringate anions constitute chains along the b axis in -A-B-A- fashion. The members of the chains are linked by through N-H ···O hydrogen bonds. The (en) molecules are responsible for connecting adjacent layers.

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