The use of Direct Phasing Methods for Single Crystal Electron Diffraction Data. I. Methylene Subcells

1976 ◽  
Vol 34 ◽  
pp. 544-545
Author(s):  
D. L. Dorset ◽  
H. A. Hauptman
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Crystal Structure Analysis ◽  
Electron Diffraction Data ◽  
Trial And Error ◽  
Mosaic Crystals ◽  
Crystal Electron ◽  
Kinematical Theory

The significant impediment to the use of electron diffraction data for crystal structure analysis is, of course, the perturbation of n-beam dynamical effects. In more severe cases this dynamical perturbation gives an intensity distribution in the diffraction pattern which is not directly related to the underlying crystal structure, thus making the determination of complex structures nearly impossible by this technique.However, as was experimentally established in Vainshtein's laboratory and is theoretically predicted, the diffraction of electrons from thin mosaic crystals composed of light atoms is in accord with kinematical theory to a good first approximation and, furthermore, ab initiocrystal structure analyses are tractable viastandard crystallographic phase determination. To date the few electronographic determinations of unknown organic structures have used either trial and error or Patterson techniques.

scholarly journals Ab-initio crystal structure analysis and refinement approaches of oligo p-benzamides based on electron diffraction data

2012 ◽  
Vol 68 (2) ◽  
pp. 171-181 ◽  
Author(s):  
Tatiana E. Gorelik ◽  
Jacco van de Streek ◽  
Andreas F. M. Kilbinger ◽  
Gunther Brunklaus ◽  
Ute Kolb
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Electron Diffraction ◽  
Ab Initio ◽  
Structure Analysis ◽  
Diffraction Data ◽  
Crystal Structure Analysis ◽  
Electron Diffraction Data ◽  
Perfect Agreement ◽  
Bonding Scheme

Ab-initio crystal structure analysis of organic materials from electron diffraction data is presented. The data were collected using the automated electron diffraction tomography (ADT) technique. The structure solution and refinement route is first validated on the basis of the known crystal structure of tri-p-benzamide. The same procedure is then applied to solve the previously unknown crystal structure of tetra-p-benzamide. In the crystal structure of tetra-p-benzamide, an unusual hydrogen-bonding scheme is realised; the hydrogen-bonding scheme is, however, in perfect agreement with solid-state NMR data.

Ab initio structure determination of interlayer expanded zeolites by single crystal rotation electron diffraction

2014 ◽  
Vol 43 (27) ◽  
pp. 10593-10601 ◽  
Author(s):  
Peng Guo ◽  
Leifeng Liu ◽  
Yifeng Yun ◽  
Jie Su ◽  
Wei Wan ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Ab Initio ◽  
Diffraction Data ◽  
Structure Determination ◽  
Electron Diffraction Data ◽  
Crystal Rotation ◽  
Ab Initio Structure ◽  
Crystal Electron

Rotation electron diffraction (RED) combines the beam tilt and goniometer tilt to obtain single crystal electron diffraction data, which has been used forab initiostructure determination of interlayer expanded zeolites.

Daliranite, PbHgAs2S5: determination of the incommensurately modulated structure and revision of the chemical formula

2019 ◽  
Vol 75 (4) ◽  
pp. 711-716 ◽  
Author(s):  
Arianna E. Lanza ◽  
Mauro Gemmi ◽  
Luca Bindi ◽  
Enrico Mugnaioli ◽  
Werner H. Paar
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Structural Model ◽  
Electron Diffraction Data ◽  
Chemical Formula ◽  
Modulated Structure ◽  
X Ray

The incommensurately modulated crystal structure of the mineral daliranite has been determined using 3D electron diffraction data obtained on nanocrystalline domains. Daliranite is orthorhombic with a = 21, b = 4.3, c = 9.5 Å and shows modulation satellites along c. The solution of the average structure in the Pnma space group together with energy-dispersive X-ray spectroscopy data obtained on the same domains indicate a chemical formula of PbHgAs2S5, which has one S fewer than previously reported. The crystal structure of daliranite is built from columns of face-sharing PbS8 bicapped trigonal prisms laterally connected by [2+4]Hg polyhedra and (As3+ 2S5)4− groups. The excellent quality of the electron diffraction data allows a structural model to be built for the modulated structure in superspace, which shows that the modulation is due to an alternated occupancy of a split As site.

Crystal Packing of Odd-Chain Saturated Triglycerides

1983 ◽  
Vol 38 (7-8) ◽  
pp. 511-514 ◽  
Author(s):  
Douglas L. Dorset
Keyword(s):  
Crystal Structure ◽  
Melting Point ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Crystal Packing ◽  
Electron Diffraction Data ◽  
Chain Packing ◽  
Crystal Electron ◽  
First Time ◽  
End Group

Single crystal electron diffraction data from an odd-chain triglyceride, glycerol triheptadecanoate, are compared with the known structure of the even-chain homo-acid triglycerides. Both class­es of triglycerides are found to resemble one another in chain packing: they both have the same chain tilt (61 °) for the β-polymorph and, further, the orientation of the T∥ subcell in the crystal structure is identical. The existence of the T∥ subcell is quantitatively verified for the first time with the diffraction intensities from suitably tilted crystals. Given these similarities in β-poly­morph structure, the major difference between triglycerides with even or odd chains (indicated by published long spacing and melting point alternation) must be due to the methyl end group pack­ing - i.e., the end group packing volume for the odd-chain glycerides must be larger than found for the even-chain materials.

Crystal Structure Determination of Glycerol-Containing Lipids from Electron Diffraction Data. Use of Analog Compounds Based upon Configurational Isomers of Cyclopentane-1, 2, 3-TRIOL

1977 ◽  
Vol 35 ◽  
pp. 24-25
Author(s):  
Douglas L. Dorset ◽  
Anthony J. Hancock
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Crystal Surface ◽  
Coherent Scattering ◽  
Crystal Structure Determination ◽  
Electron Diffraction Data ◽  
Polar Group ◽  
Axis Orientation

Lipids containing long polymethylene chains were among the first compounds subjected to electron diffraction structure analysis. It was only recently realized, however, that various distortions of thin lipid microcrystal plates, e.g. bends, polar group and methyl end plane disorders, etc. (1-3), restrict coherent scattering to the methylene subcell alone, particularly if undistorted molecular layers have well-defined end planes. Thus, ab initio crystal structure determination on a given single uncharacterized natural lipid using electron diffraction data can only hope to identify the subcell packing and the chain axis orientation with respect to the crystal surface. In lipids based on glycerol, for example, conformations of long chains and polar groups about the C-C bonds of this moiety still would remain unknown.One possible means of surmounting this difficulty is to investigate structural analogs of the material of interest in conjunction with the natural compound itself. Suitable analogs to the glycerol lipids are compounds based on the three configurational isomers of cyclopentane-1,2,3-triol shown in Fig. 1, in which three rotameric forms of the natural glycerol derivatives are fixed by the ring structure (4-7).

scholarly journals Procedure and Computer Programs for the Structure Determination of Gaseous Molecules from Electron Diffraction Data.

1969 ◽  
Vol 23 ◽  
pp. 3224-3234 ◽  
Author(s):  
B. Andersen ◽  
H. M. Seip ◽  
T. G. Strand ◽  
R. Stølevik ◽  
Gunner Borch ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Computer Programs ◽  
Electron Diffraction Data
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