STRATEGY determines a starting spindle angle for efficient data collection. It is written for 1-circle diffractometers with 2D-detectors. Given an initial crystal orientation, the initial spindle angle, the wavelength, crystal to detector distance, the direct beam position on the detector and some detector parameters, it will simulate all the reflections that will occur if the crystal is rotated 360 degrees. Given the space group symmetry, the program determines for each possible starting spindle the amount of degrees needed to get (by default) 100%, 99%, 98%, 97%, 96% or 95% of all the unique reflections. (The desired completeness can be specified by the user as well.) A redundancy table will be calculated for each of the smallest oscillation ranges possible.
The program reads the information concerning the initial crystal orientation, the initial spindle angle, etc. from a DENZO x-file, which is produced by indexing a (first) diffraction image, refining it, and integrating it using the command calculate go. The name of the x-file has to be specified in the input file for STRATEGY.
STRATEGY simulates only those reflections that diffract between the specified resolution limits, and determines for each reflection whether it can be recorded on the detector or not. It takes into account any misorientation of the detector ( cassette rotx roty rotz) and any horizontal or vertical shift ( x beam y beam).
Mosaicity, beam divergence or any other convolution are not taken into account! This means that the reflections are simulated to diffract as delta functions. This will not harm the prediction of the ideal spindle angle as long as the simulation of the spots in DENZO using the correct mosaicity does not lead to overlaps. This has to be checked! The number of overlaps will also be influenced by the oscillation range. Find an oscillation range that does not give overlaps (coloured red in XDISPLAYF), but still gives a reasonable number of fully recorded reflections (coloured green in XDISPLAYF). Then one or two degrees additional oscillation on both edges of the advised oscillation range should be added in order to make sure that all the reflections that were recorded only partly in the vincinity of the starting and ending spindle angle can be recorded completely.
The program handles both all the 11 Laue groups and the 32 point groups. This means that the simulations can be done for anomalous data collection as well.
The program works in batch mode. An input file is needed in which the name of the x-file is specified together with the space group number or name and the format of the detector. Optionally, the number of bins and the name of the Postscript file produced by the program can be specified, together with some other options. The program will only test the first four characters of each command in the input file. The commands are not case sensitive: the program will convert all the commands to uppercase. A maximum of one command on each line can be given. If a line starts with the character > then the program will consider that line as a comment.
The program runs for a DIP2000 detector and the small and big MAR detector. The program has been tested for: