An X-ray study of the crystal-structure of antigorite (With Plate V)

1945 ◽  
Vol 27 (188) ◽  
pp. 65-74 ◽  
Author(s):  
Endel Aruja
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Line Broadening ◽  
X Ray ◽  
Complete Determination

Antigorite is a lamellar variety of serpentine, and is supposed to be a dimorphous form of chrysotile, which is finely fibrous. Its chemical composition is approximately H4Mg3Si2O9, which is taken as the basis of calculations here.This study was undertaken primarily because it was hoped that knowledge of the structure of antigorite would throw some light on that of chrysotile. Certain similarities between the two structures have been established, namely in the c(7·3kX or 14·6kX), and b(9·2kX) directions. There are two main differences, however. Firstly, imperfections which cause line broadening in the X-ray pattern of chrysotile, are absent in antigorite (apart from certain ‘streaks’). Secondly, the a(43·4kX) axis of antigorite is approximately eight times longer than the corresponding axis in chrysotile. A complete determination of the structure has not been achieved, but the X-ray pattern has been described, and some suggestions made as to the explanation of the peculiarities observed. A further study of the outstanding questions is in progress.

The crystal-structure and optical properties of matlockite (PbFCl)

1934 ◽  
Vol 23 (146) ◽  
pp. 587-597 ◽  
Author(s):  
F. A. Bannister
Keyword(s):  
Crystal Structure ◽  
Optical Properties ◽  
Chemical Composition ◽  
Chemical Analysis ◽  
Single Crystal ◽  
British Museum ◽  
Museum Collection ◽  
X Ray ◽  
Fluorine Determination

It has recently been shown by W. Nieuwenkamp that matlockite is identical in chemical composition and crystal-structure with artificial lead fluochloride PbFC1. His conclusion is based upon powder photographs of the two substances and a fluorine determination of a specimen of matlockite from Matlock, Derbyshire. The present work was undertaken primarily to check Nieuwenkamp's interesting results. Access to an exceptionally fine suite of matlockite specimens in the British Museum collection made possible single crystal X-ray measurements, accurate optical determinations, and a new chemical analysis.

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.

The protonation of the ethylenediphosphinetetraacetate anion and the crystal structure of the bis (hydrogen bromide) of ethylenediphosphinetetraacetic acid

1981 ◽  
Vol 46 (12) ◽  
pp. 3063-3073 ◽  
Author(s):  
Jana Podlahová ◽  
Bohumil Kratochvíl ◽  
Vratislav Langer ◽  
Josef Šilha ◽  
Jaroslav Podlaha
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Structure Determination ◽  
Free Acid ◽  
Hydrogen Bromide ◽  
Carboxyl Groups ◽  
Spectroscopic Methods ◽  
X Ray ◽  
Partial Formation

The equilibria and mechanism of addition of protons to the ethylenediphosphinetetraacetate anion (L4-) were studied in solution by the UV, IR, 1H and 31P NMR spectroscopic methods. A total of six protons can be bonded to the anion. They are added stepwise, first with partial formation of zwitterions containing P-H bonds, which then dissociate with formation of the free acid, H4L, where all four protons are bonded in carboxyl groups. The formation of zwitterions is strongly dependent on the concentration. In the final stage, the acid bonds two additional protons to form the bis-phosphonium cation, H6L2+. A number of isostructural salts containing this cation, H4L.2 HX (X = Cl, Br, I), have been prepared. The X-ray crystal structure determination of the bromide confirmed the expected arrangement. The bromide crystals are monoclinic, a = 578.2, b = 1 425.0, c = 1 046.7 pm, β = 103.07° with a space group of P21/c, Z = 2. The final R factor was 0.059 based on 1 109 observed reflections. The structure consists of H6L2+ cations containing protons bonded to phosphorus atoms (P-H distance 134 pm) and of bromide anions, located in gaps which are also sufficiently large for I- anions in the isostructural iodide. The interbonding of phosphonium cations proceeds through hydrogen bonds, C-OH...O=C, in which the O...O distance is 275.3 pm.

Crystal structure determination of the conformation of two bicyclo[3.3.1]nonan-ones

1985 ◽  
Vol 63 (6) ◽  
pp. 1166-1169 ◽  
Author(s):  
John F. Richardson ◽  
Ted S. Sorensen
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Molecular Structures ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Final Agreement

The molecular structures of exo-7-methylbicyclo[3.3.1]nonan-3-one, 3, and the endo-7-methyl isomer, 4, have been determined using X-ray-diffraction techniques. Compound 3 crystallizes in the space group [Formula: see text] with a = 15.115(1), c = 7.677(2) Å, and Z = 8 while 4 crystallizes in the space group P21 with a = 6.446(1), b = 7.831(1), c = 8.414(2) Å, β = 94.42(2)°, and Z = 2. The structures were solved by direct methods and refined to final agreement factors of R = 0.041 and R = 0.034 for 3 and 4 respectively. Compound 3 exists in a chair–chair conformation and there is no significant flattening of the chair rings. However, in 4, the non-ketone ring is forced into a boat conformation. These results are significant in interpreting what conformations may be present in the related sp2-hybridized carbocations.

scholarly journals Preparative-scale HPLC Resolution of Metallacyclic η3-Allyltricarbonyliron Complexes and Determination of the Absolute Configuration by X-Ray Crystal Structure Analysis

1999 ◽  
Vol 23 (9) ◽  
pp. 578-579
Author(s):  
Rainer Schobert ◽  
Hermann Pfab ◽  
Jutta Böhmer ◽  
Frank Hampel ◽  
Andreas Werner
Keyword(s):  
Crystal Structure ◽  
Silica Gel ◽  
Structure Analysis ◽  
Absolute Configuration ◽  
Crystal Structure Analysis ◽  
Preparative Scale ◽  
X Ray ◽  
The Absolute

Racemates of (η3-allyl)tricarbonyliron lactone complex Fe(CO)3{η1:η3-C(O)XCH2CHCMeCH2} 1a (X = O) and (η3-allyl)tricarbonyliron lactam complex 2a (X = NMe) are resolved on a preparative scale by HPLC on cellulose tris(3,5-dimethylphenyl)carbamate/silica gel RP-8 and the absolute configuration of (-)-2a is determined by X-ray crystal structure analysis.

Crystal structure determination of solar cell materials: Cu2ZnSnS4 thin films using X-ray anomalous dispersion

2012 ◽  
Vol 524 ◽  
pp. 22-25 ◽  
Author(s):  
Hiroshi Nozaki ◽  
Tatsuo Fukano ◽  
Shingo Ohta ◽  
Yoshiki Seno ◽  
Hironori Katagiri ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Solar Cell ◽  
Structure Determination ◽  
Anomalous Dispersion ◽  
Crystal Structure Determination ◽  
X Ray

The Use of the Pseudo-Voigt Function in the Variance Method of X-ray Line-Broadening Analysis

1997 ◽  
Vol 30 (4) ◽  
pp. 427-430 ◽  
Author(s):  
F. Sánchez-Bajo ◽  
F. L. Cumbrera
Keyword(s):  
Crystallite Size ◽  
Original Form ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Variance Method ◽  
The Mean ◽  
Voigt Function

A modified application of the variance method, using the pseudo-Voigt function as a good approximation to the X-ray diffraction profiles, is proposed in order to obtain microstructural quantities such as the mean crystallite size and root-mean-square (r.m.s.) strain. Whereas the variance method in its original form is applicable only to well separated reflections, this technique can be employed in the cases where there is line-profile overlap. Determination of the mean crystallite size and r.m.s. strain for several crystallographic directions in a nanocrystalline cubic sample of 9-YSZ (yttria-stabilized zirconia) has been performed by means of this procedure.

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