[phenixbb] generate Rfree flag for twinned crystals with 3 twin fractions

[Zheng Zhou]

Dear all

After reading the informative posts in mailing list, I started to deal
with my first twinning dataset. The space group is P3. Xtriage found 3
twin laws. R vs R statistics indicated perfect twinning for two twin
laws and one is twin with RPS. I realize that twin-related reflections
should be in the same work or free group. Could phenix handle the
Rfree flag correctly for me when there are more than one twin fraction
identified?

By applying one twin law, the Rfree dropped from 37% to 28% using
phenix. When I use Refmac, the twin fractions are refined and the
Rfree is down to 26%. I copied the Rfree flag from phenix to the ccp4
in this case. When I let ccp4 generate Rfree flag automatically, the
Rfree is refined to 26% too. Should I label the Rfree at a higher
space group?

Thanks for your advice

Best,

Zheng (Joe) Zhou