Crystallographic Information Framework

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Index

Protein Data Bank exchange dictionary (pdbx) version 1.0521

_pdbx_reflns_twin.mean_F_square_over_mean_F2

Name:
'_pdbx_reflns_twin.mean_F_square_over_mean_F2'

Definition:

   
The ideal statistics for twinned crystals. The values calculated with the
acentric data are given below. 

Statistic	Untwinned data	Perfect twinned data
<I^2>/<I>^2	2.0             1.5
<F>^2/<F^2>	0.785           0.865

References:
 Yeates, T.O. (1997) Methods in Enzymology 276, 344-358. Detecting and
     Overcoming Crystal Twinning.

 and information from the following on-line sites:
   CNS site http://cns.csb.yale.edu/v1.1/
   CCP4 site http://www.ccp4.ac.uk/dist/html/detwin.html
   SHELX site http://shelx.uni-ac.gwdg.de/~rherbst/twin.html


Type: float

Mandatory item: yes

Category: pdbx_reflns_twin