On Tue, Jun 22, 2010 at 11:09 PM, <colin.n...@diamond.ac.uk> wrote: > My interest was really what happened in the observed diffraction > pattern. With the large difference in the orthorhombic cell dimensions, > the spots will gradually separate for the higher orders. The point I > really wanted to discuss was whether there would be an advantage if one > could distinguish the spots and measure the intensity of each component. > I am sure one could do this - the question I had was whether it would be > useful.
My experience with pseudo-merohedral twinning (it was actually the reticular case with half the spots overlapped and the other non-overlapped half on a pseudo C-centred lattice) is that the degree of splitting varies widely over the diffraction pattern. In some places there was complete overlap, in others you see elongation of the spots, in others partial separation, and in others complete separation (and of course all shades in-between), with around 50-50 intensity split. In this situation the mosaicity becomes meaningless! I'm not aware of any software that can handle this kind of thing successfully (and certainly the data we did manage to get turned out to be garbage!). Cheers -- Ian
