PMID: 9175261May 1, 1997Paper

The accurate electron crystallographic refinement of organic structures containing heavy atoms

Acta Crystallographica. Section A, Foundations of Crystallography
D L Dorset

Abstract

Prospects for the accurate structure determination of heavy-atom-containing organic crystals were evaluated with electron diffraction data from perchloro and perbromo derivatives of copper phthalocyanine. While the extensive overlap of experimental Patterson maps (from 1200kV intensities) with respective crystal autocorrelation functions explains the success of previous direct structure analyses, it is clear that multiple-scattering perturbations still evident at high voltage will frustrate the determination of accurate bond distances and angles. If, however, the result obtained after direct structure analysis and Fourier refinement is used to position an idealized molecular model (i.e. with chemically reasonable bonding parameters), the correct structure can then be justified by a rotational search coupled with a multislice dynamical calculation. Even though dynamical scattering is not the only major perturbation to such data sets, the resolution-limited correction is still sufficient to identify the correct molecular orientation in the unit cell. Alternatively, an acceptable unconstrained structure refinement can be carried out via a procedure proposed by Huang, Liu, Gu, Xiong, Fan & Li [Acta Cryst. (1996), A52, 152-157]. A p...Continue Reading

Citations

Mar 21, 2007·Microscopy and Microanalysis : the Official Journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada·Masanori KoshinoSeiij Isoda
Jan 24, 2007·Ultramicroscopy·Douglas L Dorset
Dec 3, 2014·Ultramicroscopy·Ganesh SubramanianJohn C H Spence
Jan 31, 2015·Micron : the International Research and Review Journal for Microscopy·Yumei WangGuangcan Che

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