An X-ray Lab-Based Tutorial and Structure Determination Demo
by Michael J. Vela, Tae H. Cho
and Bruce M. Foxman
This tutorial was written with the advanced high school science student in mind. Since most high school chemistry classes only briefly discuss aspects of crystal structure, the goal of this tutorial is to extend the subject to a demonstration of the practical operations of X-ray diffraction and structure determination. While it is important to us that the tutorial be a stand-alone educational tool, we hope that, on suitable occasions, small groups of high school students, accompanied by their teachers, will visit Prof. Foxman’s X-ray lab (or another lab closer to home) for a field trip. In preparation for the trip, students would have completed some or all of the tutorial and have grown crystals of citric acid or sucrose. A suitable crystal would be selected from the batch, mounted on the diffractometer, and solved in a few hours’ time. We believe this will provide an enrichment opportunity for students and teachers alike. Version 1.01 of the tutorial contains > 110 PowerPoint "slides", as well as a large number of external links. Connection to the internet is not required to use the tutorial, as the links are included with the distribution.
In a chemistry course students learn about types of bonding, bond distances and angles, Lewis Dot Structures and VSEPR. How were the distance and angle values determined? How do we know how the atoms are connected in a molecule? Can we “see” atoms? The technique of X-ray structure determination provides both insight and answers to these questions. This practical tutorial is designed to show the operations involved in taking a crystal of a common compound, such as sucrose or citric acid, and determining its structure using X-rays. There are also slides, links, and “side trips” to help with some of the fine points. Going straight through the show, without the side trips, will provide an excellent idea of just what an “X-ray crystallographer” does every day (but do visit the “extras” for the best experience). Today, the technique of X-ray structure determination is extremely important in many fields, including chemistry, materials science, pharmaceuticals and the structure determination of proteins.
Support by the National Science Foundation through grants DMR-0504000 and CHE-0521047 is gratefully acknowledged.
Version 1.01 INCLUDES ALL EXTERNAL LINKS. The inclusion of links was made in response to comments from users of the University-level Space Groups and Symmetry tutorial, available on this site, that links soon became outdated or changed. The “notes” section on each slide includes the complete references to the links bundled with this version. In order for the bundled links to run successfully, the tutorial must be installed in a specific directory (C:\insights). Full instructions are given below.
The tutorial will run on a PC or Mac with MS PowerPoint installed. The download is a compressed .zip file.
Please fill in these details to help us track usage of the program. You will not be sent unsolicited email. You may be notified of important updates if you request them by leaving the check in the box below:
Once the .zipped file above has been downloaded, the tutorial must be installed in the specific directory “C:\Insights”. A shortcut provided in that directory may then be moved to the desktop if desired, or the program may be run directly from the directory by double-clicking on the shortcut in the directory. Note that the folder "Main" must appear at the top level of the Insights directory, or all links will be broken. The tutorial contains historical and pedagogic links; browser behavior varies with version and "brand". Returning to the tutorial from the browser seems to work best in Mozilla/Netscape by minimizing the browser window. In IE, return to the tutorial works best using a right-click, and selecting "Back". Let us know if there are any problems. The tutorial links have been tested with only the latest versions of browsers. If erratic behavior is encountered, that is a source to consider.
There is a price for using this tutorial!!!! Please send feedback with corrections, suggestions, etc. We hope you will enjoy this material and will find it useful.
Michael J. Vela
Send content and tutorial comments to Bruce M. Foxman ( foxman1 at brandeis.edu)
Bruce Foxman ( foxman1 at brandeis.edu ) Last updated 16 February 2007