Thanks to all who responded to my somewhat uninformative posting. Here are some references that were provided on what is most likely a lattice translocation disorder in one direction in these crystals,
Porta et al. 2009 (Acta Cryst. D67, 628-638) Wagner et al., 2009, Acta Cryst. B65, 249-268 Sauter et al. 2010 (Acta Cryst. D43, 611-616) Wang et al., 2005, Acta Cryst. D61, 67-74 Laurie Betts On Mon, Apr 7, 2014 at 7:26 AM, Ivan Campeotto <[email protected]>wrote: > Dear Laurie, > > I think you may be dealing with a modulated structure, superposition of > multiple lattices or a lattice-translocation defect, it is hard to judge > based only on the diffraction pattern profile. > For the first case, I would suggest to have a look at Porta et al. 2009 > (Acta Cryst. D67, 628-638), where they describe the usage of Eval15 to > process the data. In this scenario, the position of the satellite > reflections can be described by an extra vector q, which can have from 1 to > 3 components and it is added to the canonical scattering vector S (see also > Wagner et al., 2009, Acta Cryst. B65, 249-268). However, from your image, > the spots are not resolved inside the streaks, indicating that perhaps this > is not the case. > For the second case, I would recommend Sauter et al., 2010 (Acta Cryst. > D43, 611-616), where the usage of LABELIT is described to deal with > superposed lattices. > For the third possible case, the lattice-traslocation defects, it is > important to define how a translocation can occur between the two lattices > (see details in Wang et al., 2005, Acta Cryst. D61, 67-74). Their > diffraction images look very similar to yours. > > You do not comment whether you were able to perform data reduction. I > suspect that it would be rather difficult, although the integration > programs may reject the streaks at a certain price in terms of integration > statistics etc. > In any case I would recommend to deal with the issue as early as possible, > i.e. data collection stage or indexing stage, to avoid of carrying the > problem over into the next steps of structure solution / structure > refinement. > Out of curiosity, it would be nice to know the appearance of the streaks, > if you collect data with fine slicing (i.e by using a Pilatus detector) or > with a kappa goniometer (you may have already done this of course). > Do you see these streaks in all crystal orientations? > Can you resolve spots within the streaks and what is your resolution? > > Good luck! > > Best wishes > > Dr. Ivan Campeotto > Imperial College London > London, UK >
