Twin Detection with Improved Robustness

The twin statistic calculated here is based on local intensity differences making it less sensitive to phenomena that tend to confound traditional intensity statistics, such as anisotropic diffraction and pseudo-centering.

Reference: J. Padilla & T. O. Yeates. A statistic for local intensity differences: robustness to anisotropy and pseudo-centering and utility for detecting twinning. Acta Crystallogr. D59, 1124-30, 2003.

For more information on both types of twinning the please see the Introduction to Hemihedral Twinning.

This twinning test was implemented with the program "dataman" available from the Uppsala Software Factory.

This is Version 4. Versions 2 and 3 are no longer in service.

Comments and Questions on the Twinning Server may be sent to: yeates at
Please send any Problems with the website to: holton at

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Perform the Twin Test on Your Data
Indicate the format of the input structure factors
CNS/X-PLOR format F and sigma(F) must be labeled "FOBS" and "SIGMA"
free format h, k, l, F, and sigma(F) read in free format
Input file upload
Indicate the space group




Perform Twinning Analysis
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