Hi Graeme, > On 21 Feb 2024, at 16:52, Winter, Graeme (DLSLtd,RAL,LSCI) > <00006a19cead4548-dmarc-requ...@jiscmail.ac.uk> wrote: > > Processing a data set in lower than necessary symmetry e.g. tetragonal as > monoclinic you _cannot_ import the merged MTZ file into i2 because it is > impossible to have 90 degree angles for P21
I had a look at the code in CCP4i2 that generates the errors in the screenshots you posted. The first one is only generated if two cell parameters are *exactly* equal and the second is generated when beta is between 89.9999 and 90.0001 degrees. I think these tests should only fail if the data were processed assuming higher symmetry so that unit cell parameters were restrained and then the space group changed to a lower symmetry one. Isn't the correct approach when the true symmetry is lower than originally assumed to repeat the data processing without applying constraints imposed by the higher symmetry - because, for example, cell parameters refined assuming cell length/angle constraints may not predict the reflection positions as well as if these restraints were not applied, reflections assumed to be symmetry equivalent when they weren't may lead to suboptimal scaling etc etc? Huw ######################################################################## 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/
