Silicon-Crystal Determination of the Absolute Scale of X-Ray Wavelengths

The determination of the absolute polarity of a polar material is often crucial to the understanding of the defects which occur in such materials. Several methods exist by which this determination may be performed. In bulk, single-domain specimens, macroscopic techniques may be used, such as the different etching behavior, using the appropriate etchant, of surfaces with opposite polarity. X-ray measurements under conditions where Friedel’s law (which means that the intensity of reflections from planes of opposite polarity are indistinguishable) breaks down can also be used to determine the absolute polarity of bulk, single-domain specimens. On the microscopic scale, and particularly where antiphase boundaries (APBs), which separate regions of opposite polarity exist, electron microscopic techniques must be employed. Two techniques are commonly practised; the first [1], involves the dynamical interaction of hoLz lines which interfere constructively or destructively with the zero order reflection, depending on the crystal polarity. The crystal polarity can therefore be directly deduced from the relative intensity of these interactions.

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

Journal of Chemical Research ◽

10.1177/174751989902300930 ◽

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.

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Full-foil x-ray mapping of integrated column density applied to the absolute determination of mass attenuation coefficients

Measurement Science and Technology ◽

10.1088/0957-0233/15/9/019 ◽

2004 ◽

Vol 15 (9) ◽

pp. 1811-1822 ◽

Cited By ~ 22

Author(s):

M D de Jonge ◽

Z Barnea ◽

C Q Tran ◽

C T Chantler

Keyword(s):

Column Density ◽

Attenuation Coefficients ◽

X Ray ◽

Absolute Determination ◽

Mass Attenuation Coefficients ◽

The Absolute ◽

Mass Attenuation

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Étude conformationnelle de cétopipérazines: (I) 3R-méthyl-6-carbéthoxy-2 oxopipérazine, (II) 3R-[p-hydroxybenzyl]-6-carbéthoxy-2 oxopipérazine: I, II en solution et structure cristalline de II

Canadian Journal of Chemistry ◽

10.1139/v87-218 ◽

1987 ◽

Vol 65 (6) ◽

pp. 1308-1312 ◽

Cited By ~ 3

Author(s):

André Michel ◽

Guy Evrard ◽

B. Norberg

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Absolute Configuration ◽

Structure Determination ◽

Opiate Receptor ◽

Receptor Level ◽

X Ray ◽

Diastereomeric Mixture ◽

The Absolute

The synthesis of the title compounds has been described recently. It was anticipated that the product would be a diastereomeric mixture. Surprisingly, only one isomer was obtained. The present work is an attempt to find the conformationnal properties accounting for those observations. X-ray structure determination of 3R-[p-hydroxybenzyl]-6-carbethoxy-2-oxopiperazine shows that the molecule adopts a folded conformation and that the absolute configuration at C6 is [R]. Investigation in solution using 1H nuclear magnetic resonance shows the existence of three conformers and discusses the relative populations. Those findings are also relevant in terms of the activity of such compounds at the opiate receptor level.

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Size and Concentration Determination of Colloidal Nanocrystals by Small-Angle X-Ray Scattering

10.26434/chemrxiv.5942920 ◽

2018 ◽

Author(s):

Jorick Maes ◽

Nicolo Castro ◽

Kim De Nolf ◽

Willem Walravens ◽

Benjamin Abécassis ◽

...

Keyword(s):

Band Gap ◽

Small Angle ◽

Accurate Determination ◽

Band Gap Energy ◽

Colloidal Nanocrystals ◽

X Ray ◽

Absolute Scale ◽

X Ray Scattering ◽

Ray Scattering

<div> <div> <div> <p>The accurate determination of the dimensions of a nano-object is paramount to the de- velopment of nanoscience and technology. Here, we provide procedures for sizing quasi- spherical colloidal nanocrystals (NCs) by means of small-angle x-ray scattering (SAXS). Using PbS NCs as a model system, the protocols outline the extraction of the net NC SAXS pattern by background correction and address the calibration of scattered x-ray intensity to an absolute scale. Different data analysis methods are compared, and we show that they yield nearly identical estimates of the NC diameter in the case of a NC ensemble with a monodisperse and monomodal size distribution. Extending the analysis to PbSe, CdSe </p> </div> </div> <div> <div> <p>and CdS NCs, we provide SAXS calibrated sizing curves, which relate the NC diameter and the NC band-gap energy as determined using absorbance spectroscopy. In compari- son with sizing curves calibrated by means of transmission electron microscopy (TEM), we systematically find that SAXS calibration assigns a larger diameter than TEM calibration to NCs with a given band gap. We attribute this difference to the difficulty of accurately sizing small objects in TEM images. To close, we demonstrate that NC concentrations can be directly extracted from SAXS patterns normalized to an absolute scale, and we show that SAXS-based concentrations agree with concentration estimates based on absorption spectroscopy.</p></div></div></div>

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A chiral probe useful for optical resolution and X-ray crystallographic determination of the absolute stereochemistry of carboxylic acids

Tetrahedron Asymmetry ◽

10.1016/s0957-4166(00)80409-7 ◽

1993 ◽

Vol 4 (8) ◽

pp. 1755-1758 ◽

Cited By ~ 22

Author(s):

Nobuyuki Harada ◽

Tomomi Soutome ◽

Shinji Murai ◽

Hisashi Uda

Keyword(s):

Carboxylic Acids ◽

Optical Resolution ◽

X Ray ◽

The Absolute ◽

Absolute Stereochemistry

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Determination of the temperature and time dependence of the absolute small-angle X-ray scattering intensity of partially crystalline polymers employing synchrotron radiation

Polymer ◽

10.1016/0032-3861(89)90316-9 ◽

1989 ◽

Vol 30 (9) ◽

pp. 1582-1590 ◽

Cited By ~ 31

Author(s):

R. Gehrke ◽

C. Riekel ◽

H.G. Zachmann

Keyword(s):

Synchrotron Radiation ◽

Time Dependence ◽

Small Angle ◽

Scattering Intensity ◽

X Ray ◽

Crystalline Polymers ◽

X Ray Scattering ◽

The Absolute ◽

Ray Scattering

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Determination of the absolute stereostructure of a cyclic azobenzene from the crystal structure of the precursor containing a heavy element

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.12.212 ◽

2016 ◽

Vol 12 ◽

pp. 2211-2215 ◽

Cited By ~ 2

Author(s):

Reji Thomas ◽

Nobuyuki Tamaoki

Keyword(s):

Cd Spectroscopy ◽

Chiral Molecules ◽

X Ray Diffraction ◽

X Ray ◽

Heavy Atoms ◽

Unambiguous Determination ◽

The Common ◽

The Absolute ◽

Reverse Method

Single crystal X-ray diffraction has been used as one of the common methods for the unambiguous determination of the absolute stereostructure of chiral molecules. However, this method is limited to molecules containing heavy atoms or to molecules with the possibility of functionalization with heavy elements or chiral internal references. Herein, we report the determination of the absolute stereostructure of the enantiomers of molecule (E)-2, which lacks the possibility of functionalization, using a reverse method, i.e., defunctionalization of its precursor of known stereostructure with bromine substitution (S-(−)-(E)-1). A reductive debromination of S-(−)-(E)-1 results in formation of one of the enantiomers of (E)-2. Using a combination of HPLC and CD spectroscopy we could safely assign the stereostructure of one of the enantiomers of (E)-2, the reduced product R-(−)-(E)-1.

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