Hi everyone,
I have some question about the merging of diffraction data from
different crystals. I have two (room-temperature) datasets in my hand
and each of them can be scaled in P21 space group and the screw axis is
along k. However,each dataset only have below 55% completeness. To get
better completeness, I am trying to merge this two datasets. The problem
is one dataset has cell dimension (80.632,87.085,114.977),(90,90.026,90)
and the other one has (85.497,79.857,114.003) (90,90.004,90),. It looks
like that the a,b dimensions are switched between these two datasets.
Unsurprisingly,the chi^2 is very high when I tried to merge these two
datasets in scalepack.I am wondering whether there is any way to reindex
these two datasets to make their a/b dimensions match. Any suggestion
will be highly appreciated.
By the way, as you might notice, the beta angle is pretty close to
90 degree. I scaled the datasets into P212121 or P2221 or P21212 at the
beginning,I had no trouble to merge them in these space groups.
However,I could not make the Rfree go below 45% during following
refinement (2.7 angstrom cutoff). Phenix.xtriage indicated that there
might exist twinning but no twin law is given. Then I reindexed the data
into P2 and scaled them in P21 SG.Phenix.xtriage indicates there exists
a pseudomerohedral twinning operator. When I used the twin law given in
phenix.refine,the Rfree could go down to 29%. So I think P21 might be
the correct space group.
Thanks again for any suggestion.
Yuan