Hi Generally, choose the one that has the beta closest to 90º - correlations between a* and c* are minimised. Both cells have the same volume, but one “leans over” more than the other.
Harry > On 10 Nov 2025, at 10:20, Dawn Duan > <[email protected]> wrote: > > Dear community members, > > I recently received a different opinion regarding whether one sample should > be C121 or I121. > > I am trying to integrate automatic data processing and displaying resutls to > users. In the pipeline, I run pointless to get the best space group solution, > in the end of this message comes the detailed pointless output related to > space group determination that I got for one of the samples. I took the best > solution from pointless, i.e. I121 (Cell: 81.74 67.10 86.75 > 90.00 98.20 90.00). However, I later also extracted the space group and > unit cell result from the phenix.xtriage output and got C121 (Cell: 110.377 > 67.1 81.744 90 128.931 90). The space group number indicates space group 5 > from both cases, and according to the International Tables for > Crystallography Volume A: Space-group symmetry Second online edition (2016) > [ISBN: 978-0-470-97423-0 (https://it.iucr.org/services/purchase/)[doi: > 10.1107/97809553602060000114](http://dx.doi.org/10.1107/97809553602060000114), > space group 5 should be C121. > > Could I receive some wisdom from the community regarding whether one is > correct, and if so, which one, or whether both are correct? Any further > comments/opinion regarding whether I should display both options (I121 and > C121 with their corresponding unit cell parameters) would be helpful. > > Thank you so much in advance! > > Best, > Dawn > > pointless output: > <!--SUMMARY_BEGIN--> > > Input file is merged so subgroups of the input symmetry are omitted > Only groups of the same or higher symmetry are kept > WARNING: very low completeness 0.38 in merged file, may not be able to > determine Laue group > > > Laue Group Lklhd NetZc Zc+ Zc- CC CC- Rmeas R- Delta > ReindexOperator > > = 1 I 1 2/m 1 *** 1.000 8.53 8.53 0.00 0.85 0.00 0.07 0.00 0.0 > [-l,k,h+l] > > > <!--SUMMARY_END--> > > ******************************************************** > > Testing Lauegroups for systematic absences > ------------------------------------------ > > No systematic absence zones to test in this lattice group > > Time for systematic absence tests: 0.053 secs > > > Possible spacegroups: > -------------------- > Indistinguishable space groups are grouped together on successive lines > 'Reindex' is the operator to convert from the input hklin frame to the > standard spacegroup frame. > 'TotProb' is a total probability estimate (unnormalised) > 'SysAbsProb' is an estimate of the probability of the space group based on > the observed systematic absences. > 'Conditions' are the reflection conditions (absences) > Spacegroup TotProb SysAbsProb Reindex Conditions > > I 1 2 1 ( 5) 1.000 1.000 [-l,k,h+l] > > > --------------------------------------------------------------- > > > Space group confidence (= Sqrt(Score * (Score - NextBestScore))) = 1.00 > Laue group confidence (= Sqrt(Score * (Score - NextBestScore))) = 1.00 > Selecting space group I 1 2 1 as there is a single space group with the > highest score > <!--SUMMARY_BEGIN--> $TEXT:Result: $$ $$ > Best Solution: space group I 1 2 1 > Reindex operator: [-l,k,h+l] > Laue group probability: 1.000 > Systematic absence probability: 1.000 > Total probability: 1.000 > Space group confidence: 1.000 > Laue group confidence 1.000 > > Unit cell: 81.74 67.10 86.75 90.00 98.20 90.00 > $$ <!--SUMMARY_END--> > HKLIN spacegroup: C 1 2 1 C-centred monoclinic > The input crystal system is C-centred monoclinic > (Cell: 110.38 67.10 81.74 90.00 128.93 90.00) > The crystal system chosen for output is body-centred monoclinic > (Cell: 81.74 67.10 86.75 90.00 98.20 90.00) > > ######################################################################## > > 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/
