search site  |  contact us  HOME PRODUCTS DOWNLOADS SALES SUPPORT NEWS CrystalMaker Advice Centre   Why Doesn't My Diffraction Pattern Look Right? This is a common query for most automated diffraction programs. In almost all cases, problems relate to an incorrectly-defined symmetry set and/or the underlying crystal structure... In an ideal world, one would be able to go direct from, say, a crystal structures database, to a simulated diffraction pattern in CrystalDiffract. In practise, one has to exercise a degree of caution. It is, sadly, not at all unusual for database files (whether they be in CIF, FDAT, etc. format) to contain errors, or to be mis-formatted. When simulating diffraction patterns from such data, the results are, at best, unpredictable, and at worst, completely wrong. As the old maxim goes, "Garbage in, garbage out". We strongly encourage users to inspect structures in CrystalMaker, before proceeding to generate diffraction patterns via CrystalDiffract or SingleCrystal. This way, you can confirm that your starting parameters are at least reasonable. Tips for checking structures in CrystalMaker: If you are familiar with the structure, does the CrystalMaker model look reasonable? If you are not familiar with the structure, at least check that there are no unrealistically-close atom contacts. Check that the symmetry, listed in the Edit Crystal sheet (Edit > Structure) is correct. If your structure contains bonds, check the coordination numbers in the Atom Info window (Window > Palettes > Atom Info). Are these reasonable? Do a quick bond search, to check that atom distances are reasonable. Use the Transform > List Bonds command to search around a specific site. Check your site occupancies. Do you have the correct atoms on the right sites? Do you need to specify fractional occupancy for some (disordered) sites? If you are convinced that your structural parameters are correct - and you are still getting the wrong diffraction pattern, please contact our technical support. If necessary, feel free to e-mail any supporting files to us. We are always fully-committed to helping users resolve any problems, as quickly and easily as possible. © 2008 CrystalMaker Software Limited. All rights reserved worldwide.