Crystallography Reviews Vol. 15, No. 1, January–March 2009, 57–83
Practical suggestions for better crystal structures Peter Mu¨ller* Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
Downloaded By: [Müller, Peter] At: 18:59 22 January 2009
(Received 15 September 2008; final version received 9 October 2008) X-ray crystallography is one of the most popular analytical methods, and with the advent of area detectors in the 1990s single crystal X-ray structure determination has become commonplace. Initially, the method was reserved for the expert, but hard- and software improvements of the last couple of decades have enabled scientists who are not formally trained in crystallography to determine crystal structures as well. This has led to an explosion of the number of crystal structures and, unfortunately, also of the number of incorrect structures submitted to scientific journals. It is evident that (semi)automated structure determination works only for routine structures. In more complex cases, such as structures with disorders, pseudo-symmetry or twinning, crystallographic knowledge, refinement skills and experience are still vital for obtaining high-quality, publication-grade crystal structures. This article is meant to offer a few suggestions to scientists who are using crystallography as part of their research, as an ancillary-science so to speak, hoping to help improve the quality of their crystal structures. Keywords: structure refinement; crystal growth; data collection strategy; structure solution; restraints; constraints; disorder
Contents
page
1. Introduction
58
2. Pre-refinement strategies 2.1. Crystal growth and crystal handling 2.2. Choosing a crystal, mounting and diffractometer alignment 2.3. Data collection strategy 2.4. Absorption correction 2.5. Structure solution
58 59 60 61 62 62
3. Structure refinement 3.1. Parameters 3.2. Constraints 3.3. Restraints 3.4. General strategies
63 63 64 65 69
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[email protected] ISSN 0889–311X print/ISSN 1476–3508 online ß 2009 Taylor & Francis DOI: 10.1080/08893110802547240 http://www.informaworld.com
