I guess you must have CCP4 software installed? Try setting up a project with CCP4I2 and running the task under Xray data reduction and analysis Data reduction - AIMLESS
This will give you a detailed report on possible spacegroups and indexing.. Very helpful for a beginner! On Fri, 17 Jul 2026 at 08:03, Kay Diederichs < [email protected]> wrote: > Hello Jakob, > > The highest-possible crystal symmetry should always be used, in order to > make the description of the experiment as simple (parsimonious) as possible. > > In my book, the R-values you report are the "same" for P21 and P212121 > ("same" meaning "similar enough to be explained by different choice of free > reflections, and different degrees of freedom resulting from having twice > as many atoms"). That means that the higher symmetry is the correct one. > > Just note that you can _always_ refine in a lower-symmetry subgroup, > without really changing the scientific insight from the experiment. > P21 is a subgroup of P212121. Note that in your case, you can choose the > unique axis of P21 in three ways - you chose one of them. The other two > should give similar R-values. > You could even refine in P1 (of course with 4 times the number of > molecules in the ASU, compared to P212121, and twice compared to P21), > without significantly changing the R-values. > > Hope this helps, > Kay > > ######################################################################## > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > > This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a > mailing list hosted by www.jiscmail.ac.uk, terms & conditions are > available at https://www.jiscmail.ac.uk/policyandsecurity/ > ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
