XRayView
A Teaching Aid for X-Ray Crystallography

Introduction

XRayView Version 2.1 uses interactive computer graphics to introduce basic concepts of X-ray diffraction by crystals, including the reciprocal lattice, the Ewald sphere construction, Laue cones, the wavelength dependence of the reciprocal lattice, primitive and centered lattices and systematic extinctions, rotation photography, Laue photography, space group determination and Laue group symmetry, and the alignment of crystals by examination of reciprocal space.

XRayView is designed with "user-friendliness" in mind, using Motif style, pull-down menus to control the program. Many of the experiences of using real X-ray diffraction equipment to examine crystalline diffraction can be simulated. Exercises are available on-line to guide the users through typical X-ray diffraction experiments.

The real-time simulations require significant graphics and computational power. For this reason, this release is restricted to use on the Silicon Graphics 4D series, including the entry level Indigos, although future releases may be available for other X-based platforms.

This software is copyrighted and should not be used without recognizing the following restrictions. XRayView is free to educational institutions. Other users should contact: 

     George Phillips
     Rice University
     Dept. of Biochemistry and Cell Biology
     Mail Stop 140
     Houston, Texas, 77005-1892

     email: georgep@rice.edu
Any proceeds will be used directly for additional development of XRayView.

Usage

Type xrayview to start the program. Use the EXERCISE and HELP menus to go from there.

Known problems

If the wavelength is very small and the resolution very high, so many reciprocal lattice points are generated that the program becomes intolerably slow.

Customizing

If you wish, you can control certain aspects of the program by means of UNIX environment variables. The default values are stored in /remote/local/bin/xrayview. To change these values, type the following: 
setenv XrayDir xrayview_directory 
setenv XrayExerText pathname
setenv XrayMaxHKL value 
setenv LaueMin  value 
setenv LaueMax value 
setenv LaueIncrFloor value 
setenv LaueIncrPct value 
/remote/model/xrayview/xrayview
The 7 environment variables are used as follows:
XrayDir
the default directory for opening files. default = /remote/model/XRayView
XrayExerText
the default pathname for the exercise text file. The exercise text file for this version is stored at /remote/model/XRayView/Exercise.txt
XrayMaxHKL
an arbitrary number, representing the maximum number of points in the reciprocal lattice to be examined. If this number is exceeded, the program reduces the resolution, to keep the wait-time for calculation reasonable. If you have a very fast machine, you may wish to experiment with this value. default = 12000.
LaueMin and LaueMax
Min/max values for the wavelength sweep for Laue photographs. default = 0.5 and 2.0 respectively.
LaueIncrFloor and LaueIncrPct
These variables control the increment during the Laue sweep. The increment is equal to a percentage of the wavelength, but not less than the floor. default = 0.012 and 1.0 respectively.
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Last updated: 01/23/2001