[phenixbb] Refining f'/f"?

Nathaniel Echols NEchols at lbl.gov
Thu May 7 12:52:11 PDT 2009

On May 7, 2009, at 3:39 PM, Leigh Allen wrote:
> I collected at 1.0809A, which was the optimal wavelength for the  
> beam at NSLS-X29.  I will model them as MSEs.  I guess the better  
> question to ask is if I should be concerned with not having these  
> negative peaks.  Will it negatively affect my R-work/R-free if I  
> continue to work with the data that's not been scaled to keep F+/F-  
> separate?

At that wavelength f' is approximately -2 and f'' is 0.6, which are  
much less than at the Se K edge:


I would expect R/Rfree to improve slightly if you refine against F+/ 
F-, but if you do this and still see negative peaks, I wouldn't worry  
about them.  (Note: you still need to scale your data, just don't  
average F+/F- - in HKL2000 clicking the "Anomalous" box in the scaling  
window is sufficient.)

Nathaniel Echols
Lawrence Berkeley Lab
NEchols at lbl.gov

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