Notizen: Über zwei Bleiantimonphosphate mit Eulytinstruktur: Pb3SbIII(PO4)3 und Pb11SbV(PO4)9/On two Lead Antimony Phosphates with Eulytine Structure: Pb3SbIII(PO4)3 and Pb11SbV(PO4)9

1980 ◽  
Vol 35 (6) ◽  
pp. 771-772 ◽  
Author(s):  
Günter Engel ◽  
Jutta Belgardt
Keyword(s):  
Cell Volume ◽  
Lattice Constant ◽  
Thermal Behaviour ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Large Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Stereochemical Activity ◽  
Characteristic Manner

Abstract Two lead antimony phosphates have been prepared, which both crystallize with the cubic eulytine structure. Pb3SbIII(PO4)3 has the lattice constant a= 1037.2 pm and Pb11SbV(PO4)9 has a = 1037.5 pm. The X-ray diffraction diagrams appear nearly identical. In their chemical and thermal behaviour these compounds differ in a characteristic manner, however. The relatively large cell volume of Pb3Sb(PO4)3 is attributed to the very distinct stereochemical activity of the lone electron pair of Sb3+.

Structure of russellite (Bi2WO6): origin of ferroelectricity and the effect of the stereoactive lone electron pair on the structure

2018 ◽  
Vol 74 (3) ◽  
pp. 295-303 ◽  
Author(s):  
Hiroki Okudera ◽  
Yuka Sakai ◽  
Kentaro Yamagata ◽  
Hiroaki Takeda
Keyword(s):  
Low Temperature ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Lone Pair ◽  
Orthorhombic Phase ◽  
Electrostatic Charge ◽  
X Ray Diffraction ◽  
Coordination Environment ◽  
X Ray ◽  
Powder Neutron Diffraction

The structure of the low-temperature polar (orthorhombic) phase of russellite (Bi2WO6) was examined on artificial specimens with precise single-crystal X-ray diffraction experiments. The final atomic arrangement thus obtained was identical to that reported by Knight [Miner. Mag. (1992), 56, 399–409] with powder neutron diffraction. The residual density attributable to a stereochemically-active lone pair of electrons of bismuth was prominent at approximately the centre of a larger cap of BiO8 square antiprisms, that is on the line from the Bi sites to an adjacent WO4 2− slab along the b-axis direction. Quite uneven Bi—O distances and the formation of a vacant coordination hemisphere (within 3 Å) should, therefore, be ascribed to the strong demand of bismuth to form shorter Bi—O bonds to use up its electrostatic charge within its coordination environment. The shift of bismuth along −c propagates via the correlated shift of the W site and these cooperative shifts cause ferroelectricity in the compound. This propagation was easily effected by the intrusion of molecules such as acetone into the structure.

scholarly journals Barysilite from Garpenberg Norra, Dalarna, Sweden: occurrence and crystal structure refinement

2002 ◽  
Vol 66 (2) ◽  
pp. 353-363 ◽  
Author(s):  
U. Kolitsch ◽  
D. Holtstam
Keyword(s):  
Crystal Structure ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Divalent Cations ◽  
Structure Refinement ◽  
Direct Proof ◽  
Structural Formula ◽  
X Ray Diffraction ◽  
X Ray ◽  
Area Detector

AbstractA new occurrence of barysilite, Pb8Mn(Si2O7)3, at the polymetallic Garpenberg Norra Zn-Pb deposit, Hedemora, Dalarna, Sweden, is described. The mineral, which forms colourless, transparent grains, is characterized by X-ray diffraction and electron-microprobe analyses. The assemblage includes tephroite, zincian jacobsite, manganoan diopside and others. The crystal structure of a barysilite crystal from Garpenberg Norra was redetermined using single-crystal X-ray diffraction data (Mo-Kα, CCD area detector) and has been refined in space group R3̄c with a = 9.804(1), c = 38.416(8)Å, V = 3197.8(8)Å3, to R1 = 2.32% for 1025 ‘observed’ reflections with Fo >4σ(Fo). A previous, low-precision structure determination (Lajzérowicz, 1965; R = 20%) is confirmed but improved considerably. The structure contains one distorted MnO6 polyhedron with six equivalent Mn–O bonds (2.224 Å), one Si2O7 disilicate unit with an Si–O–Si angle of 120.9°, and two non-equivalent Pb sites. The Pb1 site has a highly irregular, one-sided coordination with six O ligands, indicating a stereoactive 6s2 lone-electron pair on the Pb2+ ion, whereas the [6+3]-coordinated Pb2 site is fairly regular, with Pb–O distances of 2.540 (3×), 2.674 (3×) and 3.098 (3×) Å. The Pb2 site contains ~10% of Ca (+Ba) replacing Pb, corresponding to the structural formula Pb16(Pb,Ca)22Mn(Si2O7)3. This is the first direct proof that not only the M site in barysilite-type Pb8M(Si2O7)3 compounds can be replaced by divalent cations.

scholarly journals Crystal Structure of the Disordered Non-Centrosymmetric Compound Fe0.43Mo2.56SbO9.5

Crystals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 40
Author(s):  
Sk Ali ◽  
Sven Lidin ◽  
Mats Johnsson
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Building Blocks ◽  
Fold Axis ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters

Single crystals of Fe0.43Mo2.56SbO9.5 were obtained by hydrothermal techniques at 230 °C. The crystal structure was determined from single crystal X-ray diffraction data. The compound crystallizes in the non-centrosymmetric space group Pc with unit cell parameters a = 4.0003(2) Å, b = 7.3355(3) Å, c = 12.6985(6) Å, β = 90°. The crystal structure comprises five crystallographically independent M atoms and one Sb3+ atom, M atoms are of two kinds of partially occupied sites Mo6+ and Fe3+. The building blocks consist of [SbO3O0.5O0.5E] octahedra (E = lone electron pair) and [(Mo/Fe)O6] octahedra. The M = (Mo, Fe) and O atoms are arranged in a distorted hexagonal 2D-net, not the Sb atoms. The distortion of the net and consequently the symmetry reduction results mainly from the location of the Sb atoms. Disorder manifests itself as a splitting of the metal sites and as a consequent shortening of the Mo–Fe distances. Six (Mo/Fe)O6 octahedra are connected to form a pseudohexagonal channel. The Sb3+ atom is displaced from the pseudo-six-fold axis.

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 Metal-Rich Metallaboranes: Synthesis, Structures and Bonding of Bi- and Trimetallic Open-Faced Cobaltaboranes

Inorganics ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 28
Author(s):  
Kriti Pathak ◽  
Chandan Nandi ◽  
Jean-François Halet ◽  
Sundargopal Ghosh
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Room Temperature ◽  
Electron Pair ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Cluster 2 ◽  
Cobalt Center

Synthesis, isolation, and structural characterization of unique metal rich diamagnetic cobaltaborane clusters are reported. They were obtained from reactions of monoborane as well as modified borohydride reagents with cobalt sources. For example, the reaction of [Cp*CoCl]2 with [LiBH4·THF] and subsequent photolysis with excess [BH3·THF] (THF = tetrahydrofuran) at room temperature afforded the 11-vertex tricobaltaborane nido-[(Cp*Co)3B8H10] (1, Cp* = η5-C5Me5). The reaction of Li[BH2S3] with the dicobaltaoctaborane(12) [(Cp*Co)2B6H10] yielded the 10-vertex nido-2,4-[(Cp*Co)2B8H12] cluster (2), extending the library of dicobaltadecaborane(14) analogues. Although cluster 1 adopts a classical 11-vertex-nido-geometry with one cobalt center and four boron atoms forming the open pentagonal face, it disobeys the Polyhedral Skeletal Electron Pair Theory (PSEPT). Compound 2 adopts a perfectly symmetrical 10-vertex-nido framework with a plane of symmetry bisecting the basal boron plane resulting in two {CoB3} units bridged at the base by two boron atoms and possesses the expected electron count. Both compounds were characterized in solution by multinuclear NMR and IR spectroscopies and by mass spectrometry. Single-crystal X-ray diffraction analyses confirmed the structures of the compounds. Additionally, density functional theory (DFT) calculations were performed in order to study and interpret the nature of bonding and electronic structures of these complexes.

Study of Thermal Behaviour of EPDM/SBR Blends and Carbon Nanocoatings Deposited by Sputtering

2021 ◽  
Vol 875 ◽  
pp. 116-120
Author(s):  
Muhammad Alamgir ◽  
Faizan Ali Ghauri ◽  
Waheed Qamar Khan ◽  
Sajawal Rasheed ◽  
Muhammad Sarfraz Nawaz ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Weight Loss ◽  
Thermogravimetric Analysis ◽  
Thermal Behavior ◽  
Thermal Behaviour ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Stability Of

In this study, the effect of SBR concentration (10 Phr, 20 Phr & 30 Phr ) on the thermal behavior of EPDM/SBR blends was studied. Thermogravimetric analysis (TGA) was used to check weight loss of samples as function of temperature by heating upto 600°C. X-ray diffraction (XRD) was performed to determine quality and % crystallinity of the elastomer blends. It was seen that % crystallinity improved with an increase in the content of SBR in EPDM/SBR blends. TGA revealed that the thermal stability of EPDM/SBR blends has improved by 17% than neat EPDM. Carbon nano-coatings produced by sputtering have no beneficial influence on thermal behaviour of elastomers.

Darstellung und Kristallstruktur von Tl4TiS4, TI4SnS4 und Tl4TiSe4 / Preparation and Crystal Structure of Tl4TiS4, TI4SnS4 and Tl4TiSe4

1984 ◽  
Vol 39 (6) ◽  
pp. 705-712 ◽  
Author(s):  
Kurt O. Klepp ◽  
Günther Eulenberger
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Structures ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Monoclinic System ◽  
The Mean ◽  
Similar Description ◽  
Oriented Parallel ◽  
Stereochemical Activity

AbstractThe isostructural compounds Tl4TiS4, Tl4SnS4 and Tl4TiSe4 crystallize in the monoclinic system, space group P21/c with a = 8.328, b = 8.191, c = 15.248 Å, β = 104.53°; a = 8.395, b = 8.280, c = 15.398 A, ft = 103.69°, and a = 8.517, b = 8.389, c = 15.672 Å, β = 103.50°, respectively. There are four formula units in the unit cell. The crystal structures were determined and refined from single crystal diffractometer data. They are characterized by isolated tetrahedral thioanions which are connected with each other by Tl+ ions. The mean bond lengths are Ti-S = 2.26 Å, Sn-S = 2.40 Å and Ti -Se = 2.38 Å. The Tl atoms are surrounded by six and seven chalcogen atoms, respectively, in an irregular and polar arrangement, thus indicating stereochemical activity of the lone electron pair of the Tl+ ions. Tl-S distances vary from 2.93 to 3.98 Å, Tl-Se distances from 3.03 to 3.96 Å. The Tl atoms have nearest Tl neighbours at distances ranging from 3.46 to 3.65 Å. The crystal structure can be described as built from pseudotetragonal slabs oriented parallel to (001) which contain the cations and the tetrahedral anions. It is shown that a similar description is valid also for the crystal structures of Tl4GeS4 [1] and Na4SnS4 [2, 3].

Cyclic hexapeptoids with N-alkyl side chains: solid-state assembly and thermal behaviour

CrystEngComm ◽  
2020 ◽  
Vol 22 (38) ◽  
pp. 6371-6384 ◽  
Author(s):  
Giovanni Pierri ◽  
Rosaria Schettini ◽  
Jürgen Nuss ◽  
Robert E. Dinnebier ◽  
Francesco De Riccardis ◽  
...  
Keyword(s):  
Solid State ◽  
Thermal Behaviour ◽  
Lattice Energy ◽  
Side Chains ◽  
X Ray Diffraction ◽  
Energy Calculations ◽  
X Ray ◽  
Alkyl Side Chains

The solid state assembly of two cyclic hexapeptoids decorated respectively with five and six carbon N-alkyl side chains is analyzed by X-ray diffraction, intermolecular energies and lattice energy calculations.

EPITAXY OF ULTRATHIN CoO FILMS STUDIED BY XPD AND GIXRD

2002 ◽  
Vol 09 (02) ◽  
pp. 937-941 ◽  
Author(s):  
P. LUCHES ◽  
C. GIOVANARDI ◽  
T. MOIA ◽  
S. VALERI ◽  
F. BRUNO ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Lattice Constant ◽  
Photoelectron Spectroscopy ◽  
Grazing Incidence ◽  
X Ray Diffraction ◽  
Direction Parallel ◽  
X Ray ◽  
Photoelectron Diffraction ◽  
Rocksalt Structure ◽  
Plane Lattice

CoO layers have been grown by exposing to oxygen the (001) body-centered-tetragonal (bct) surface of a Co ultrathin film epitaxially grown on Fe(001). Different oxide thicknesses in the 2–15 ML range have been investigated by means of synchrotron-radiation-based techniques. X-ray photoelectron spectroscopy has been used to check the formation of the oxide films; X ray photoelectron diffraction has given information concerning the symmetry of their unit cell; grazing incidence X-ray diffraction has allowed to evaluate precisely their in-plane lattice constant. The films show a CoO(001) rocksalt structure, rotated by 45° with respect to the bct Co substrate, with the [100] direction parallel to the substrate [110] direction. Their in-plane lattice constant increases as a function of thickness, to release the in-plane strain due to the 3% mismatch between the bulk CoO phase and the underlying substrate.

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