I obviously didn't pay any attention to the specific numbers/space group (and didn't read the rest of your message). Fred is absolutely right - the only thing you can do in P21 is to switch a and c (and invert b to maintain the right hand).
So maybe your crystal can be indexed both ways, but denzo picks a random solution. If playing with reference zone doesn't help, try autoindexing using different images, more/fewer peaks, different values for spot size and resolution cutoffs... What you basically are trying to do is to shake denzo into choosing the right solution. On Thu, 2009-10-22 at 17:32 +0200, Vellieux Frederic wrote: > Hi Yuan, > > I think you cannot merge the 2 data sets if the space group is indeed > P21. If you have systematic extinctions along the b* axis both on the > data set with b=87.085 and with b=79.857 then the crystals are simply > different. > > Fred. > > Yuan Cheng wrote: > > 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). --
