Dittrich, Birger (2021) On modelling disordered crystal structures through restraints from molecule-in-cluster computations,and distinguishing static and dynamic disorder. IUCrJ, International Union of Crystallography Journal , 8. pp. 305-318. ISSN 2052-2525

Abstract

Distinguishing disorder into static and dynamic based on multi-temperature
X-ray or neutron diffraction experiments is the current state of the art, but is
only descriptive, not predictive. Here, several disordered structures are revisited
from the Cambridge Crystallographic Data Center ‘drug subset’, the Cambridge
Structural Database and own earlier work, where experimental intensities of
Bragg diffraction data were available. Using the molecule-in-cluster approach,
structures with distinguishable conformations were optimized separately, as
extracted from available or generated disorder models of the respective
disordered crystal structures. Re-combining these ‘archetype structures’ by
restraining positional and constraining displacement parameters for conventional
least-squares refinement, based on the optimized geometries, then often
achieves a superior fit to the experimental diffraction data compared with
relying on experimental information alone. It also simplifies and standardizes
disorder refinement. Ten example structures were analysed. It is observed
that energy differences between separate disorder conformations are usually
within a small energy window of RT (T = crystallization temperature). Further
computations classify disorder into static or dynamic, using single experiments
performed at one single temperature, and this was achieved for propionamide.

Item Type:	Article
Keywords:	quantum crystallography; crystal structures; disorder refinement; molecule-in-cluster optimizations.
Date Deposited:	24 Mar 2021 00:45
Last Modified:	24 Mar 2021 00:45
URI:	https://oak.novartis.com/id/eprint/43371