R-Value and Free R-Value

Rob Hooft Rob.Hooft at embl-heidelberg.de
Tue Nov 26 07:23:57 EST 1996


>>>>> "DB" == Ditlev Brodersen <ditlev at kemi.aau.dk> writes:

 DB> The definition is
 DB>       sum(num(num(Fo)-k*num(Fc))) 
 DB>   R = ---------------------------
 DB>             sum(num(Fo))

 DB> where sum is a sum over all Miller indices h, k, l. 

Unfortunately, the sum is not a sum over all Miller indices hkl, but
rather a sum over all Miller indices hkl for which an observation
exists, and for which the crystallographer has decided to use it 
[like I>2sigma(I)]. This is one of the reasons R is not as useful as it
may seem to judge the quality of the model.

Regards,

-- 
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