[phenixbb] unit cell discrepancies

Pavel Afonine pafonine at lbl.gov
Thu Apr 21 12:23:51 PDT 2011

Hi Dale,

>     This would not work because the cell constants are highly correlated
> with the other parameters in the model.  You have to change the cell,
> refine all the other parameters, and then write down the R value.  Many
> people have become confused by performing the test you describe.  It shows
> a very steep dependency between the R value and the cell constants but
> the lowest R value is always at the values for the cell the model was
> refined with.  If you perform your grid test and refine at each step
> you will see the broad minimum.
> Dale Tronrud

realizing it, this is why I refixed my reply with "Not going into 
discussion whether this would be beneficial or not" -:)

By suggesting this test I was thinking to catch some gross errors in 
unit cell parameters (that were probably not compensated by refinement 
of other parameters). My previous experience with some other similar 
searches tells me that you can find almost everything in this database.


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