scholarly journals On the Nature of the Spin Frustration in the CuO2Ribbon Chains of LiCuVO4: Crystal Structure Determination at 1.6 K, Magnetic Susceptibility Analysis, and Density Functional Evaluation of the Spin Exchange Constants

2011 ◽  
Vol 50 (8) ◽  
pp. 3582-3588 ◽  
Author(s):  
Hyun-Joo Koo ◽  
Changhoon Lee ◽  
Myung-Hwan Whangbo ◽  
Garry J. McIntyre ◽  
Reinhard K. Kremer
Keyword(s):  
Crystal Structure ◽  
Magnetic Susceptibility ◽  
Structure Determination ◽  
Density Functional ◽  
Spin Exchange ◽  
Crystal Structure Determination ◽  
Functional Evaluation ◽  
Spin Frustration ◽  
Susceptibility Analysis ◽  
Exchange Constants

Combined powder X-ray diffraction data and quantum-chemical calculations in EXPO2014

2017 ◽  
Vol 32 (S1) ◽  
pp. S123-S128 ◽  
Author(s):  
Angela Altomare ◽  
Fulvio Ciriaco ◽  
Corrado Cuocci ◽  
Aurelia Falcicchio ◽  
Flavio Fanelli
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Quantum Chemical ◽  
Density Functional ◽  
Structural Model ◽  
Crystal Structure Determination ◽  
Powder Diffraction Data ◽  
Quantum Chemistry Calculations

This paper describes new features implemented in the EXPO2014 software and aimed at assisting crystallographers in the use of quantum-chemistry calculations in combination with experimental powder diffraction data. The implemented tools are useful in particular in two important steps of the process of crystal structure determination from powder diffraction data: (1) preparing accurate structural model suitable for crystal structure determination by real-space methods; (2) validating structure determination. The combination of experimental/quantum-chemical methods in EXPO2014 is now managed easily thanks to the following capabilities: (a) converting crystallographic data in input files and reading molecular geometry from output files of a wide variety of computational chemistry packages (GAMESS-US, NWChem, Gaussian, CRYSTAL, ABINIT, QUANTUM ESPRESSO); (b) optimizing the geometry of a molecule using Open Babel's force fields; (c) a graphical interface to run semi-empirical quantum calculation by MOPAC (Molecular Orbital PACkage); (d) producing input file for dispersion-corrected density functional theory.

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).

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