Can data quality affect R,Rfree difference?

Raman barani at
Thu Sep 12 14:52:17 EST 1996

 Can the quality of data affect the difference between Rw and Rf ?

 Here are some details:

 I have a structure that is correct. The Rw and Rf are 20.0 and 26.0.
 The binding metal is cadmium.

 After I substitute the metal by zinc, I collected data, refined
 the structure against the new data (after simulated annealing).
 The Rw and Rf are 20.0 and 34.0.

 The resolution range, WA and almost all parameters remain the
 same, except for metal. The data showed a different R-merge
 while merging the frames. R-merge for old data-set = 5.0 and 
 R-merge for new dataset = 8.0.

 Thanks for your time. 

 Best Regards to everyone.

 -barani at

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