Wechselwirkungen in Molekülkristallen, 156 [1, 2]. Kristallzüchtung und Strukturbestimmung von (Imidodiphosphat)-Alkalisalzen mit Kationen niedriger und hoher Koordinationszahlen / Interaction in Molecular Crystals, 156 [1, 2]. Crystal Growth and Structure Determination of Alkali(imidodiphosphate) Salts with Cations of Low and High Coordination Numbers

2000 ◽  
Vol 55 (9) ◽  
pp. 773-784 ◽  
Author(s):  
Hans Bock ◽  
Erik Heigel ◽  
Norbert Nagel
Keyword(s):  
Crystal Growth ◽  
Coordination Number ◽  
Molecular Crystals ◽  
Chelating Ligands ◽  
Chain Polymer ◽  
Coordination Numbers ◽  
Structural Differences ◽  
A Chain ◽  
High Coordination

Imidodiphosphates ⊖N[PO(OR)2]2 and Imidodiphosphonates ⊖N[POR2]2 are effective chelating ligands for a variety of metal cations including even Na⊕, for which a lipophilically wrapped hexameric polyion cluster has been structurally characterized. The corresponding hexameric lithium and polyrubidium ion complexes reported here exhibit considerable structural differences: The rather small Li⊕ cations of coordination number five and tetraphenylimidodiphosphate form an isolated hexameric aggregate analogous to the Na⊕ one, whereas the larger Rb⊕ with coordination number seven and (3,4-dimethylphenyl)substituents crystallizes as a chain polymer. Based on the crystal structures, the dominant Coulomb attractions between cations and anions, the spatial requirement of the ligands and the essential phenyl/phenyl interactions in their lipophilic skin are discussed

Zur Kristallchemie der Wasserstoff–Sauerstoff-Bindungen

1994 ◽  
Vol 209 (1) ◽  
Author(s):  
H. Alig ◽  
J. Lösel ◽  
M. Trömel
Keyword(s):  
Coordination Number ◽  
Inorganic Compounds ◽  
Close Correlation ◽  
Coordination Numbers ◽  
High Coordination

AbstractThe interdependence of hydrogen – oxygen distances in inorganic compounds can be described by a close correlation if sufficiently high coordination numbers for hydrogen are taken into account. For this purpose, the coordination is favourably defined as chemical coordination number

scholarly journals On the Determination of Coordination Numbers of Coupled DEM-DFN Model for Modeling Fractured Rocks

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaoyi Xu ◽  
Li-Yun Fu ◽  
Ning Liu ◽  
Tongcheng Han
Keyword(s):  
Coordination Number ◽  
Fractured Rocks ◽  
Granular Media ◽  
Simple Formulation ◽  
Coordination Numbers ◽  
System A ◽  
Window Selection ◽  
Set Up ◽  
Dfn Model

Natural fractured rocks usually contain background granular media and multi-scale fractures. The coordination number is a crucial factor to characterize the connection of microstructural elements. The determination of coordination numbers for modeling fractured rocks is essential to interpret the distribution of cracks related to micromechanical properties. We have built a consistent workflow of discrete element models (DEMs) coupled with discrete fracture networks (DFNs). This DEM-DFN model could provide a simple formulation for high calculation efficiency to model a more realistic and detailed description of fracture system. A series of numerical experiments are set up, aiming to correlate window radius, particle size, and crack length, which will benefit the window selection for measuring coordination numbers based on the crack characteristics. The coordination number determined in the DEM-DFN modeling can be used to identify crack patterns in the spatial distribution.

Wechselwirkungen in Molekülkristallen, 174 [1, 2]. Kristallzüchtung und Strukturbestimmung verschiedenartig Methyl-substituierter Imidodiphosphorsäuretetraphenylester / Interaction in Molecular Crystals, 174 [1, 2]. Crystal Growth and Structure Determination of Differently Methyl-Substituted Tetraphenyl Imidodiphosphates

2001 ◽  
Vol 56 (6) ◽  
pp. 469-482 ◽  
Author(s):  
Hans Bock ◽  
Erik Heigel
Keyword(s):  
Crystal Growth ◽  
Structure Determination ◽  
Molecular Crystals ◽  
Structural Data ◽  
Structural Motif ◽  
Cesium Salts ◽  
Hydrogen Bonded

Abstract Four differently methyl-substituted tetraphenyl imidodiphosphates [(H3C)nC6H5-n]2PO-NH-PO[C6H5-n(C3)n] (n = 1, 2), i. e. the 4-, 3,4-, 3,5-and 2,3-derivatives, have been crystallized and their structures determined to gain information on the spatial requirements as ligands in the corresponding cesium salts. According to the packing coefficients calculated from the structural data, they increase in the sequence 4<3,5<3,4<2,3. The most perturbed structural motif is the hydrogen bonded, eight-membered of each the dimer subunits.

Human Prothrombin Activation: Determination of Plasma and Serum Levels of Prothrombin Fragment 3 by Radioimmunoassay

1979 ◽  
Author(s):  
Daniel Walz ◽  
Thomas Brown
Keyword(s):  
Blood Clotting ◽  
Factor Xa ◽  
Heart Association ◽  
Serum Levels ◽  
Cross Reactivity ◽  
Assay Procedure ◽  
A Chain ◽  
Prothrombin Activation ◽  
Theoretical Amount

Human prothrombin activation is unique in that, in addition to the release of fragment 1.2 (FI.2) from the NH-terminus of prothrombin by factor Xa during the generation of thrombin, an additional 13 residue polypeptide, fragment 3 (F3), is autocatalytically removed from the amino-terminus of the thrombin A chain. We have developed a rapid radioimmunoassay for human F3 which incorporates short incubation times and the use of a preprecipitated second antibody; the assay can be performed in three hours. Specificity studies in buffer systems show prothrombin and prethrombin 1 cross-reacting at a level of 0.001; purified thrombin does not cross-react. In the presence of 5% BSA, prothrombin displays considerably less cross-reactivity. No immunoreactive material to F3 antibodies could be detected in 400 μL of plasma. Serum, obtained from whole blood clotting, contained measurable quantities of F3 (40-100 ng/mL). This amount in serum represents only 5-10% of the theoretical amount available should all of the fragment be hydrolytically cleaved during the conversion of prothrombin to thrombin. This assay procedure is currently being utilized to monitor the activation of purified human prothrombin in the absence and presence of selected plasma inhibitors. (Supported in part by NIH 05384-17 and the Michigan Heart Association).

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

An X-ray and Neutron Scattering Study of the Structure of Zinc Vanadate Glasses

2001 ◽  
Vol 56 (6-7) ◽  
pp. 478-488
Author(s):  
Uwe Hoppe ◽  
Rainer Kranold ◽  
Emil Gattef ◽  
Jörg Neuefeind ◽  
David A. Keen
Keyword(s):  
Neutron Diffraction ◽  
Coordination Number ◽  
Short Range ◽  
Short Range Order ◽  
X Ray ◽  
Coordination Numbers ◽  
Gaussian Functions ◽  
Scattering Study ◽  
Neutron Scattering Study ◽  
Vanadate Glasses

Abstract The short-range order of vitreous V20 5 and of three (Zn0)Jt(V20 5)1_x glasses with x = 0.2, 0.4, and 0.5 is studied by X-ray and neutron diffraction experiments where the change of the contrast allows to resolve the V -0 and Z n -0 correlations. The V -0 and the Z n -0 first-neighbor peaks are approximat­ ed by several Gaussian functions. In case of vitreous V20 5 two obvious V -0 distances exist which are related with V 0 4 and V 0 5 units. With ZnO additions the V -O coordination number decreases from 4.4 in vitreous V20 5 to 4.0 in the metavanadate glass where the strongest decrease of the fraction of V 0 5 units is found for glasses of * < 0.2. Dominantly, the V 0 5 groups are linked with the neighboring units by comers. The Z n-0 coordination numbers of the modified glasses are about five with closest dis­ tances of = 0.200 nm.

Wechselwirkungen in Molekülkristallen, 160 [1,2]. Kristallzüchtung und Strukturbestimmung der verschiedenartigen Polyphenyl-Kontaktionenmultipel [p-Quaterphenylee⊖⊖][Na⊕(DME)3]2, [p-Quaterphenyl⊖⊖(Na⊕(THF)3)2] und [p-Terphenyl⊖⊖Na⊕(DME)2Na⊕(DME)]2 / Interaction in Molecular Crystals, 160 [1, 2]. Crystallization and Structure Determination of the Different Polyphenyl Contact Ion Multiples [p-Quaterphenylee⊖⊖][Na⊕(DME)3]2, [p-Quaterphenyl⊖⊖(Na⊕(THF)3)2] und [p-Terphenyl⊖⊖Na⊕(DME)2Na⊕(DME)]2

2000 ◽  
Vol 55 (12) ◽  
pp. 1103-1113 ◽  
Author(s):  
Hans Bock ◽  
K. Gharagozloo-Hubmann ◽  
M. Sievert
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Sodium Salt ◽  
Structure Determination ◽  
Metal Cation ◽  
Molecular Crystals ◽  
Sodium Salts ◽  
Structure Determinations ◽  
Cation Coordination

The π-hydrocarbons p-terphenyl and p-quaterphenyl are reduced to their dianions in aprotic solutions of different ethers at sodium metal mirrors. Single crystal structure determinations of the solvent-separated or solvens-shared contact ion multiples, [p-terphenyl⊖⊖ Na⊕(DME)2Na⊕DME]2, p-quaterphenyl⊖⊖ ][Na⊕(DME)3]2 and [p-quaterpheny⊖⊖( Na⊕(THF)3)2], prove the essential cation solvation by the chelating dimethoxyethane (DME) versus the bulky tetrahydrofuran (THF) ligands: The solution network of equilibria between solvent separated and solvent shared ion aggregates can be considerably and transparently modified by the ether solvent selected. In addition, the structures of the monomeric sodium salts reveal partly novel details of metal cation coordination by contacts Na⊕ ··· O as well as Na⊕ ··· Cπ such as in the dimeric sodium salt of p-terphenyl dianion, [(DME)2Na⊕ (terphenyl⊖⊖)(Na⊕ DME)(terphenyl⊖⊖)Na⊕ (DME)2].

The first coordination number for liquid metals

2004 ◽  
Vol 82 (4) ◽  
pp. 291-301 ◽  
Author(s):  
J R Cahoon
Keyword(s):  
Distribution Function ◽  
Radial Distribution Function ◽  
Coordination Number ◽  
Liquid Metals ◽  
Liquid Density ◽  
Isotropic Liquid ◽  
Coordination Numbers ◽  
Solid Structure ◽  
Atomic Diameter ◽  
Liquid Element

A simple and absolute method for the calculation of the first coordination number for any pure, isotropic liquid element is presented. The liquid density and the position for the first peak of the radial distribution function, assumed to be the atomic diameter, are the only parameters required. The coordination number for liquid metals that exhibit a BCC (body-centred cube) solid structure averages 7.4 while the first coordination number for liquid metals with a FCC (face-centred cube) or CPH (close-packed hexagonal) solid structure averages 7.1. Those liquid elements that have less closed-packed solid structures have a first coordination number less than 7.0. The calculation also correctly predicts the first coordination number for liquid Se to be 2.4, consistent with its chain-like structure. The calculated values for the liquid element coordination numbers are consistent with the decrease in density of a few percent that occurs upon melting and appear to be related to the Engel–Brewer valence of the solid, which suggests that the electron structure of the solid may be retained upon melting. The first coordination numbers for liquid Ge and Si were calculated to be 5.0 and 4.7, respectively, larger than the value of 4.0 for solid structures. The increase in coordination number upon melting accounts for the increase in density of Ge and Si that occurs upon melting.PACS No.: 61.20.Gy

A-Pr2S3, D-Ho2S3 und E-Yb2S3:Synthese und Einkristallstrukturuntersuchungen / A-Pr2S3, D-Ho2S3 and E-Yb2S3:Synthesis and Single Crystal Structure Investigations

1996 ◽  
Vol 51 (5) ◽  
pp. 733-738 ◽  
Author(s):  
Thomas Schleid ◽  
Falk Lissner
Keyword(s):  
Crystal Structure ◽  
Crystal Growth ◽  
Single Crystals ◽  
Alkali Halides ◽  
Structural Investigations ◽  
Coordination Numbers ◽  
Trivalent Lanthanides ◽  
Trivalent Cations ◽  
Structure Investigations ◽  
Type Orthorhombic

The oxidation of reduced chlorides (MCl2) or chloride-hydrides (MClHx) of the lanthanides with sulfur (700-850 °C, 7 d, sealed tantalum capsules or evacuated silica vessels) usually results in the formation of the sesquisulfides M2S3 as the main products. In the presence of appropriate fluxes (e.g., alkali halides), the products often are obtained as single crystals, and the flux decides which modification is favoured. Ternary halides of the trivalent lanthanides with the corresponding alkali metal can mostly be found as the second components. Crystal growth and structural investigations of thus produced single crystals of Pr2S3 (from PrClH0.67 + S + NaCl, 5:5:1, A type: orthorhombic, Pnma (No. 62), Z = 4, a = 748.22(5), b = 405.51(3), c = 1560.74(9) pm, R = 0.024, Rw = 0.020), Ho2S3, (from U - Ho2S3, + KI, 1:1, D type: monoclinic, P21/m (No. 12), Z = 6, a = 1746.15(9), b = 400.23(3), c = 1012.43(6) pm, β = 98.529(4)°, R = 0.041, Rw = 0.035), and Yb2S3 (from T-Yb2S3 + KI, 1:1, E type: trigonal, R3̄c (No. 167), Z = 6, a = 674.97(2), c = 1820.11(9) pm, R = 0.019, Rw = 0.018) are reported here. In accordance with the lanthanide contraction, the trivalent cations (M3+) exhibit sulfur coordination numbers of 7 and 8 in A -Pr2S3, 6 and 7 in D -Ho2S3, and 6 in E -Yb2S3 (corundum-type structure).

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