Intracrystalline Microstructure of Synthetic Merwinite

2000 ◽  
Vol 15 (7) ◽  
pp. 1570-1575
Author(s):  
Koichiro Fukuda
Keyword(s):  
Point Group ◽  
Monoclinic Space Group ◽  
High Symmetry ◽  
Fold Axis ◽  
X Ray Diffraction ◽  
Chemical Reagents ◽  
High Symmetry Phase ◽  
Combined Use ◽  
Axis Parallel ◽  
Antiphase Domains

Crystals of merwinite were prepared at 1550 °C from chemical reagents, and their intracrystalline microstructures were examined by the combined use of x-ray diffraction and optical microscopy. The crystals were composed of pseudomerohedral twins. The adjacent twin domains were related by the pseudosymmetry two-fold axis parallel to ⟨011⟩with the composition surface {811} The overall twin structure was constructed by introducing the pseudo-symmetry three-fold axis normal to (100), which must originally be a symmetry element of the former high-symmetry phase. The transition from the primitive trigonal (point group 3m) to the primitive monoclinic (space group P21/a) was accompanied by the combination of reducing the order of the point group and the change in the size of the unit cell. The order of the point group was reduced from 12 to 4, resulting in three twin domains with six different interfaces. This accounted for the experimentally observed microstructure consisting of repeated lamella twins in several orientations. Because the unit lattice translation would be lost during the transition, the formation of antiphase domains was expected. The lost translation vectors were 1/2[011], 1/2[100], and 1/2[111] resulting in four antiphase domains. As a result, the total number of domains possible in the transition was 3 × 4 = 12.

Campostriniite, (Bi3+,Na)3(NH4,K)2Na2(SO4)6·H2O, a new sulfate isostructural with görgeyite, from La Fossa Crater, Vulcano, Aeolian Islands, Italy

2015 ◽  
Vol 79 (4) ◽  
pp. 1007-1018 ◽  
Author(s):  
Francesco Demartin ◽  
Carlo Castellano ◽  
Carlo Maria Gramaccioli
Keyword(s):  
General Position ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
Fold Axis ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
Calculated Density ◽  
Aeolian Islands ◽  
Na Ions ◽  
Fossa Crater

AbstractThe new mineral campostriniite, (Bi3+,Na)3(NH4,K)2Na2(SO4)6·H2O, was found in an active fumarole (fumarole FA, temperature ∼350°C) at La Fossa Crater, Vulcano, Aeolian Islands, Sicily, Italy. It occurs on a pyroclastic breccia as white prismatic crystals up to 0.2 mm long, in association with adranosite, demicheleite-(Br), demicheleite-(I), argesite and sassolite. The mineral is monoclinic, space group: C2/c (no. 15) with a = 17.748(3), b = 6.982(1) c = 18.221(3) Å, β = 113.97(1)°, V = 2063(1) Å3 and Z = 4. The six strongest reflections in the powder X-ray diffraction pattern are: [dobs in Å (I)(hkl)] 6.396(100)(110), 7.507(75)(202), 2.766(60)(316), 3.380(57)(312), 5.677(55)(111), 3.166(50)(4 0 2). The empirical formula (based on 25 anions p.f.u.) is Bi2.41N1.52Na2.41K0.48 S6.07H8.08O25. The calculated density is 3.87 g cm–3. Using single-crystal diffraction data, the structure was refined to a final R(F) = 0.051 for 3025 independent observed reflections [I > 2σ(I)]. Campostriniite is isostructural with görgeyite and belongs to the 7.CD group of the Strunz classification system. The structure contains two independent nine-fold coordinated sites, one of them located on a two-fold axis (M1) and the other one in general position (M2) essentially occupied by Bi3+ atoms and minor amounts of Na+ ions, an eight-fold coordinated site fully occupied by Na +ions and another eight-fold coordinated site occupied by NH+4 and K+ ions; three independent sulfate anions in a general position and a water molecule coordinated to M1 and located on a two-fold axis are also present.

scholarly journals Darstellung und Kristallstruktur von [(NH3)5Rh(H7O4)Rh(NH3)5](S2O6)2,5 · H2O (1). Ein gemischtes Aquopentamminrhodium(III)-hydroxopentamminrhodium(III)- dithionat mit einer neuartigen μ-H7O4-Struktureinheit / Preparation and Crystal Structure of [(NH3)5Rh(H7O4)Rh(NH3)5](S2O6)2,5 · H2O (1). A Mixed Aquopentaamminerhodium(III)-hydroxopentaamminerhodium(III) Dithionate with a Novel μ-H7O4 Structural Unit

1988 ◽  
Vol 43 (2) ◽  
pp. 189-195 ◽  
Author(s):  
Walter Frank ◽  
Thomas Stetzer ◽  
Ludwig Heck
Keyword(s):  
Crystal Structure ◽  
Structural Unit ◽  
Small Difference ◽  
Point Group ◽  
Group Symmetry ◽  
Monoclinic Space Group ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray

The title compound 1 can be obtained from an aqueous solution of aquopentaammine rhodium(III) dithionate and hydroxopentaammine rhodium(III) dithionate. The crystal structure has been determined from single crystal X-ray diffraction data and refined to R = 0.035 for 4390 unique reflections. Crystal data: monoclinic, space group P21/c, a = 1300.9(5) pm. b = 1472.3(6) pm. c = 1478.8(9) pm, β = 106.20(4)°, Z = 4.In the crystal dinuclear rhodium cations with point group symmetry 1 (C1) are found. A central μ-H3O2-bridge is formed by strong hydrogen bonding between aquo and hydroxo ligands; this bridge is additionally coordinated by two molecules of water. The entire bridging system is therefore H7O4-(H3O2- · 2 H2O). O-O distances characterizing the strength of the three hydrogen bonds within this new kind of structural unit are O(H2O-Rh 1)-O(HO-Rh2): 248 pm. O(H2O-Rh 1)-O(H2Oa): 273 pm, O(HO-Rh2)-O(H2Ob): 287 pm. The hydrogen atoms involved in these bridges have been located. The small difference in the Rh 1-O(H2O) - (205.4(3) pm) and Rh2-O(OH)- (204.3(3) pm) distances indicates that the entire H7O4-- moiety serves as a μ-bridging unit between Rh 1 and Rh 2

Thioharnstoff-Derivate als Liganden in Eisen-Komplexen: Synthese und Kristallstrukturen von [FeI2L2], [Fe2I4L3], (L -L)2+[FeI4-]2 (L = (Me2N )2CS) und [Fe2I4(C6H10(NH-CS -NHMe)2)2] mit einer Notiz zu [FeIL3]+[Fe4S4I3L]-/Thiourea Derivatives as Ligands in Iron Complexes: Syntheses and Crystal Structures of [FeI2L2], [Fe2I4L3], (L -L)2+[FeI4-]2 (L = (Me2N )2CS) and [Fe2I4(C6H10(NH-CS -NHMe)2)2] and a Note on[FeIL3]+[Fe4S4I3L]-

1990 ◽  
Vol 45 (1) ◽  
pp. 45-52 ◽  
Author(s):  
Ulrich Bierbach ◽  
Wolfgang Saak ◽  
Detlev Haase ◽  
Siegfried Pohl
Keyword(s):  
Bond Length ◽  
Dinuclear Complex ◽  
Acetonitrile Solution ◽  
Monoclinic Space Group ◽  
Fold Axis ◽  
Tetrahedral Coordination ◽  
X Ray Diffraction ◽  
Thiourea Derivatives ◽  
Tetrahydrofuran Solution ◽  
Distorted Tetrahedral Coordination

Abstract [FeI2L2] (1) and [Fe2I4L3] (2) are obtained from the reaction o f FeI2 and 1,1,3,3-tetramethylthiourea(L) in tetrahydrofuran solution. The Fe(III) complex [FeI3L] (3) and iodine react in dichloromethane to give (L-L )2+[FeI4-]2 (4). The bidentate thiourea derivative C6H10(NH - CS -NHMe)2 (5) reacts in acetonitrile solution with Fel2 producing the dinuclearcomplex [Fe2I4(C6H10(NH - CS -NHMe)2)2] (6).1 and 2 were obtained in nearly quantitative, 4 and 6 in good (ca. 87%) yield.The structures of 1, 2 ,4 and 6 were determined from single crystal X-ray diffraction data.1 crystallizes in the monoclinic space group C 2/c with a = 1862.5(1), b = 1084.0(1), c = 1433.4(1) pm, β = 134.01(1)°. V = 1994.69 x 106 pm3, Z = 4, conventional R 0.055. The complex exhibits a two-fold symmetry and a distorted tetrahedral coordination of Fe(II).2: monoclinic, C 2/c, a = 1968.9(2), b = 902.8(1), c = 2222.4(2) pm, β = 123.35(1)°, V = 3299.91 x 106 pm3, Z = 4, conventional R 0.036. The metals of the dinuclear complex of 2 are sulfur-bridged with distorted tetrahedral coordination of Fe(II). The bridging sulfur lies on a two-fold axis.4: monoclinic, P21/c, a = 1135.3(2), b = 1791.9(5), c = 1642.1(4) pm, β = 93.53°, V = 3334.00 x 106 pm3, Z = 4, conventional R 0.044. The mean Fe -I bond length within the tetrahedral Fel4- anions is 254.1 pm. The (Me2N)2CS - S(NMe2)22+ cation exhibits a CS - SC dihedral angle of 75.9° and an S - S bond length o f 205.2(4) pm.In the dinuclear complex of 6 two bidentate ligands coordinate two FeI2 units in such a waythat a central eighteen-membered ring is formed. The complex shows a two-fold symmetry.Angles at the (pseudotetrahedral) metal range from 102.1(1) to 118.2(1)°.The reported synthetic and structural studies and the isolation of [FeIL3]+[Fe4S4I3L]- (7) indicatethat thiourea derivatives seem to be useful ligands for the stabilization o f neutral Fe -S clusters.

Die Kristallstrukturen von cis- und trans-Dichlorstilben

1984 ◽  
Vol 39 (4) ◽  
pp. 409-415 ◽  
Author(s):  
Evamarie Hey ◽  
Frank Weller ◽  
Kurt Dehnicke ◽  
Günther Maier
Keyword(s):  
Bond Length ◽  
Point Group ◽  
Unit Cell ◽  
Dihedral Angles ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Phenyl Rings ◽  
Cis And Trans

The crystal structures of cis- and trans-dichlorostilbene were determined from X-ray diffraction data, cw-dichlorostilbene crystallizes in the rhombohedral space group R3̄ with 18 formula units per unit cell (821 observed independent reflexions, R = 0.064) with the dimensions a = b = 3323, c = 601 pm, γ = 120°. The molecule corresponds to the point group C1 with a C = C bond length of 133 pm; the dihedral angles of the phenyl rings with the corresponding C = C-Cl plane are 48° and 72°, respectively. Trans-dichlorostilbene crystallizes in the monoclinic space group P21/n with two formula units per unit cell (1138 independent reflexions, R = 0.056) with the dimensions a = 572, b = 1733, c = 641 pm, β = 111°. The molecule is centrosymmetric (Ci) with a C = C bond length of 133 pm; the dihedral angle of the phenyl rings and the Cl - C = C plane is 71°. The stilbene molecules are disordered about the centre of symmetry in two orientations with the ratio 3:7.

Friedel'S law breakdown and interpretation of stacking fault images in tetrahedral semiconductors

1987 ◽  
Vol 45 ◽  
pp. 318-319
Author(s):  
Rob. W. Glaisher ◽  
A.E.C. Spargo
Keyword(s):  
Relative Phase ◽  
Point Group ◽  
Binary Compound ◽  
Stacking Fault ◽  
Fold Axis ◽  
Atom Pair ◽  
Tetrahedral Semiconductors ◽  
Group Symmetries ◽  
Thin Crystal ◽  
Phase Differences

Images of <11> oriented crystals with diamond structure (i.e. C,Si,Ge) are dominated by white spot contrast which, depending on thickness and defocus, can correspond to either atom-pair columns or tunnel sites. Olsen and Spence have demonstrated a method for identifying the correspondence which involves the assumed structure of a stacking fault and the preservation of point-group symmetries by correctly aligned and stigmated images. For an intrinsic stacking fault, a two-fold axis lies on a row of atoms (not tunnels) and the contrast (black/white) of the atoms is that of the {111} fringe containing the two-fold axis. The breakdown of Friedel's law renders this technique unsuitable for the related, but non-centrosymmetric binary compound sphalerite materials (e.g. GaAs, InP, CdTe). Under dynamical scattering conditions, Bijvoet related reflections (e.g. (111)/(111)) rapidly acquire relative phase differences deviating markedly from thin-crystal (kinematic) values, which alter the apparent location of the symmetry elements needed to identify the defect.

Symmetry breaking in convergent-beam diffraction

1989 ◽  
Vol 47 ◽  
pp. 480-481
Author(s):  
D.J. Eaglesham
Keyword(s):  
Symmetry Breaking ◽  
Point Group ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
Space Groups ◽  
Atomic Displacements ◽  
Small Probe ◽  
Phase Sensitive ◽  
Convergent Beam

Convergent Beam Electron Diffraction is now almost routinely used in the determination of the point- and space-groups of crystalline samples. In addition to its small-probe capability, CBED is also postulated to be more sensitive than X-ray diffraction in determining crystal symmetries. Multiple diffraction is phase-sensitive, so that the distinction between centro- and non-centro-symmetric space groups should be trivial in CBED: in addition, the stronger scattering of electrons may give a general increase in sensitivity to small atomic displacements. However, the sensitivity of CBED symmetry to the crystal point group has rarely been quantified, and CBED is also subject to symmetry-breaking due to local strains and inhomogeneities. The purpose of this paper is to classify the various types of symmetry-breaking, present calculations of the sensitivity, and illustrate symmetry-breaking by surface strains.CBED symmetry determinations usually proceed by determining the diffraction group along various zone axes, and hence finding the point group. The diffraction group can be found using either the intensity distribution in the discs

Hingganite-(Nd), Nd2□Be2Si2O8(OH)2, a new gadolinite-supergroup mineral from Zagi Mountain, Pakistan

2020 ◽  
Vol 58 (5) ◽  
pp. 549-562
Author(s):  
Anatoly V. Kasatkin ◽  
Fabrizio Nestola ◽  
Radek Škoda ◽  
Nikita V. Chukanov ◽  
Atali A. Agakhanov ◽  
...  
Keyword(s):  
New Mineral ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Average Chemical Composition ◽  
X Ray ◽  
Conchoidal Fracture ◽  
Icp Ms ◽  
Optical Axes ◽  
Mohs Hardness ◽  
Khyber Pakhtunkhwa Province

ABSTRACT Hingganite-(Nd), ideally Nd2□Be2Si2O8(OH)2, is a new gadolinite group, gadolinite supergroup mineral discovered at Zagi Mountain, near Kafoor Dheri, about 4 km S of Warsak and 30 km NW of Peshawar, Khyber Pakhtunkhwa Province, Pakistan. The new mineral forms zones measuring up to 1 × 1 mm2 in loose prismatic crystals up to 0.7 cm long, where it is intergrown with hingganite-(Y). Other associated minerals include aegirine, microcline, fergusonite-(Y), and zircon. Hingganite-(Nd) is dark greenish-brown, transparent, has vitreous luster and a white streak. It is brittle and has a conchoidal fracture. No cleavage or parting are observed. Mohs hardness is 5½–6. Dcalc. = 4.690 g/cm3. Hingganite-(Nd) is non-pleochroic, optically biaxial (+), α = 1.746(5), β = 1.766(5), γ = 1.792(6) (589 nm). 2Vmeas. = 80(7)°; 2Vcalc. = 84°. Dispersion of optical axes was not observed. The average chemical composition of hingganite-(Nd) is as follows (wt.%; electron microprobe, BeO, B2O3, and Lu2O3 content measured by LA-ICP-MS; H2O calculated by stoichiometry): BeO 9.64, CaO 0.45, MnO 0.10, FeO 3.03, B2O3 0.42, Y2O3 8.75, La2O3 1.63, Ce2O3 12.89, Pr2O3 3.09, Nd2O3 16.90, Sm2O3 5.97, Eu2O3 1.08, Gd2O3 5.15, Tb2O3 0.50, Dy2O3 2.50, Ho2O3 0.33, Er2O3 0.84, Tm2O3 0.10, Yb2O3 0.44, Lu2O3 0.04, ThO2 0.13, SiO2 23.55, H2O 2.72, total 100.25. The empirical formula calculated on the basis of 2 Si apfu is (Nd0.513Ce0.401Y0.395Sm0.175Gd0.145Pr0.096Dy0.068La0.051Ca0.041Eu0.031Er0.022Tb0.014Yb0.011Ho0.009Tm0.003Th0.003Lu0.001)Σ1.979(□0.778Fe2+0.215Mn0.007)Σ1.000(Be1.967B0.062)Σ2.029Si2O8.46(OH)1.54. Hingganite-(Nd) is monoclinic, space group P21/c with a = 4.77193(15), b = 7.6422(2), c = 9.9299(2) Å, β = 89.851(2)°, V = 362.123(14) Å3, and Z = 2. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 6.105 (95) (011), 4.959 (56) (002), 4.773 (100) (100), 3.462 (58) (102), 3.122 , 3.028 (61) (013), 2.864 (87) (121), 2.573 (89) (113). The crystal structure of hingganite-(Nd) was refined from single-crystal X-ray diffraction data to R = 0.034 for 2007 unique reflections with I &gt; 2σ(I). The new mineral is named as an analogue of hingganite-(Y), hingganite-(Yb), and hingganite-(Ce), but with Nd dominant among the rare earth elements.

Ten-Vertex Polyhedral Monocarbaborane Chemistry. The Novel High-Yield Formation of the Ten-Vertex closo Compound [6-(PMe2Ph)-closo-1-CB9H9] from the Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11]

1993 ◽  
Vol 58 (12) ◽  
pp. 2924-2935 ◽  
Author(s):  
Jane H. Jones ◽  
Bohumil Štíbr ◽  
John D. Kennedy ◽  
Mark Thornton-Pett
Keyword(s):  
Nmr Spectroscopy ◽  
Diffraction Analysis ◽  
High Yield ◽  
Monoclinic Space Group ◽  
The Novel ◽  
X Ray Diffraction ◽  
Metal Centre ◽  
X Ray ◽  
Yield Formation ◽  
Boiling Toluene

Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11] in boiling toluene solution results in an elimination of the platinum centre and cluster closure to give the ten-vertex closo species [6-(PMe2Ph)-closo-1-CB9H9] in 85% yield as a colourles air stable solid. The product is characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Crystals (from hexane-dichloromethane) are monoclinic, space group P21/c, with a = 903.20(9), b = 1 481.86(11), c = 2 320.0(2) pm, β = 97.860(7)° and Z = 8, and the structure has been refined to R(Rw) = 0.045(0.051) for 3 281 observed reflections with Fo > 2.0σ(Fo). The clean high-yield elimination of a metal centre from a polyhedral metallaborane or metallaheteroborane species is very rare.

scholarly journals High-pressure synthesis of REB5O8(OH)2 (RE = Ho, Er, Tm)

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Michael Zoller ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
Rare Earth ◽  
Ir Spectroscopy ◽  
Earth Metal ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Solution ◽  
Pressure Synthesis ◽  
The Rare Earth

AbstractThe rare earth oxoborates REB5O8(OH)2 (RE = Ho, Er, Tm) were synthesized in a Walker-type multianvil apparatus at a pressure of 2.5 GPa and a temperature of 673 K. Single-crystal X-ray diffraction data provided the basis for the structure solution and refinement. The compounds crystallize in the monoclinic space group C2 (no. 5) and are composed of a layer-like structure containing dreier and sechser rings of corner sharing [BO4]5− tetrahedra. The rare earth metal cations are coordinated between two adjacent sechser rings. Further characterization was performed utilizing IR spectroscopy.

Darstellung, 11B-, 13C-, 29Si-NMR- und Schwingungsspektren von Trimethylsilylmethyl-hexahydro-closo-hexaborat, [B6H6(CH2Si(CH3)3)]- sowie Kristallstruktur von [P(C6H5)4][B6H6(CH2Si(CH3)3)] / Preparation, 11B, 13C, 29Si NMR and Vibrational Spectra of Trimethylsilylmethyl-hexahydro-clo-hexaborate, [B6H6(CH2Si(CH 3)3)]-and the Crystal Structure of [P(C6H5)4] [B6H6(CH2Si(CH3)3)]

1995 ◽  
Vol 50 (7) ◽  
pp. 1025-1029 ◽  
Author(s):  
J. Baurmeister ◽  
A. Franken ◽  
W. Preetz
Keyword(s):  
Crystal Structure ◽  
Monoclinic Space Group ◽  
29Si Nmr ◽  
X Ray Diffraction ◽  
Nmr Spectrum ◽  
X Ray ◽  
Quadrupole Coupling ◽  
Stretching Vibration ◽  
Ir And Raman ◽  
C Nmr

By reaction of [N(C4H9 )4]2 [B6H6] with iodomethyl-trimethylsilane in acetonitrile a solution with trimethylsilylm ethyl-closo-hexaborate(1-)anions, [B6H6 (CH2Si(CH3)3)]-, is formed. The crystal structure of [P(C6H5 )4][B6H6(CH2Si(CH3)3)] has been determined by single crystal X-ray diffraction analysis; monoclinic, space group P21/n with a = 16.140(2), b = 11.646(8), c = 16.731(3) Å, β 109.664(11)°. The 11B NMR spectrum reveals features of a mono hetero substituted octahedral B6 cage. The 13C NMR spectrum exhibits a quartet at +0.18 ppm with 1J(C,H) = 118 Hz for the three methyl groups and a weak multiplet at -0.65 ppm for the methylene bridge due to quadrupole coupling with the boron atoms. In the 29Si NMR spectrum a decet at +2.25 ppm with 2J(C,H ) = 6.9 Hz is observed. The B -C stretching vibration is observed at 1155 cm-1 in the IR and Raman spectrum.

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