Chapter

The derivation of results

Simon Parsons and William Clegg

in Crystal Structure Analysis

Second edition

Published in print June 2009 | ISBN: 9780199219469
Published online September 2009 | e-ISBN: 9780191722516 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780199219469.003.0015

Series: International Union of Crystallography Texts on Crystallography

The derivation of results

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This chapter takes the next step beyond the refinement of a crystal structure, to look at the meaning and significance of the results. Various geometrical features can be calculated from atomic coordinates: bond lengths and angles, other interatomic distances, torsion angles, etc., all with associated standard uncertainties, the values of which are important for assessing the significance of differences. Least-squares planes can be fitted to groups of atoms, and dihedral angles calculated between pairs of planes. Various parameters are used to describe ring conformations. Hydrogen bonding is one of the intermolecular interactions for which geometrical criteria have been established. Atomic displacement parameters can be analysed in terms of correlated motion of rigid groups. Mathematical formulae are presented for many of these calculations.

Keywords: geometry; distances; angles; standard uncertainties; significance; least-squares planes; dihedral angles; conformation; hydrogen bonding; rigid body

Chapter.  6445 words. 

Subjects: Crystallography

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