On Jun 17, 2013, at 12:36 PM, Pramod Kumar <pramod...@gmail.com> wrote:
>> I have a crystal data diffracted around 2.9 A*, >> during the data reduction HKL2000 not convincingly showed the space group >> (indexed in lower symmetry p1), while the mosflm given C-centered >> Orthorhombic, and again with little play around HKL2000 given CO > > no ice ring is appeared, diffraction pattern looks ok, misindexing in any > direction is not conclusive to me (plz see the imj attachment) The diffraction does not look ok... there's hints of multiple lattices... which is not a problem if the two lattice orientations do not perfectly overlap (i.e. their spots are separable). Last I remember, HKL2000 bases its indexing on the 'strongest' spots on an image (though you could manually select spots). It could result in a misindex if the strongest spots come from separate lattices (and even worse if you have twinning/pseudosymmetry issues). Try a program that uses all spots for indexing, across all images (XDS for example) and you might get the true space group. Or if the crystal is big enough, you could try shooting it in different areas and 'searching' for a better spot to collect data. Or 'grow a better crystal'. F --------------------------------------------- Francis E. Reyes PhD 215 UCB University of Colorado at Boulder
