Absolute Structure Determination for Light Atom Structures

Absolute Structure Determination for Light Atom Structures

This webinar took place on April 07th 2014

Register to download slides & media

Watch Recording


The Flack parameter (x) has a physically meaningful value in the range of 0 to 1, and represents the fraction of the inverted model structure present in the crystal. It is important to interpret the value of the Flack parameter in the context of its standard uncertainty. Analysis shows that before any conclusions regarding absolute structure can be made, the standard uncertainty should be less than 0.1, even if a material is known to be enantiopure. Until recently this target has been difficult to achieve for crystal structures containing no atom heavier than oxygen.

This one-hour webinar will describe a number of statistical approaches to this problem which yield substantially more precise estimates of the Flack parameter. We will also discuss strategies for collecting diffraction data suitable for absolute structure determination and the ways in which the results of an absolute structure refinement can be validated.


Dr. Michael Ruf
Product Manager X-ray Crystallography US and Canada Bruker AXS Inc. Madison, WI USA
Dr. Simon Parsons
Professor of Crystallography School of Chemistry The University of Edinburgh