[phenixbb] UPDATE-- Difficult dataset and refinement--P422? I422?Twinning?

Nathaniel Echols nechols at lbl.gov
Tue May 8 10:25:01 PDT 2012

On Tue, May 8, 2012 at 10:08 AM, Kelly Daughtry <kddaught at bu.edu> wrote:
>> 1.    Is it really twinned since including twin-law in refinment gave much
>> better numbers?
>   I would say, it likely is twinned

Actually, Xtriage says not:

The results of the L-test indicate that the intensity statistics
behave as expected. No twinning is suspected.
The symmetry of the lattice and intensity however suggests that the
input space group is too low. See the relevant sections of the log
file for more details on your choice of space groups.

Twinned refinement can be deceptive because it often lowers the
R-factors even if twinning isn't present - Garib Murshudov warns about
this in his talks on the subject.


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