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Greetings all- I have a situation on my hands that is driving me nuts. My therapist tells me not to let it bother me, but it does. Here goes: I have a structure from a 10 x 10 x 120 micron U-Oxide material. Small crystal, but long counts on an APEX did the trick. The space group is Pmcn, and the cell is 7.14 15.52 22.31. My experience with these materials is that absorption is a headache no matter how you treat it. Thus I usually go with the most reasonable and painless route- this time I chose SADABS. This gives me a best Rint of 10.4 and R1 = 5.7. Not bad for these types of compounds. One oxygen atom in this model cannot be refined anisotropically. This isn't such a big deal- everyone working in U-O materials has had to use the ISOR command at some point. However, in an effort to clean things up a bit, I cut the data off at 0.8 (Mo radiation). This gives me an Rint of 9.5, R1 of 5.1 and TWO non-positive definites. I then tried to re-address the absorption by processing with SORTAV inside WINGX and the empirical absorption correction therein. This looks a lot like SADABS with a few more things to tweak. The best I could come up with was Rint = 11.0, R1 = 6.55 and NO non-positive definites (including partially occupied H2O sites!). So, my dilemma is thus- which data treatment do I go with? Option 1: decent R1 (5.7%), acceptable Rint (10.4%) and one NPD Option 2: cut off data and get a decent R1 (5.1%), better Rint (9.5%)and TWO NPDs Option 3: acceptable R1 (6.5%) and worst Rint (11%) and NO NPDs. By the way- I am very confident with the space group choice as I have put this structure through the ringer searching for pseudo and missing symmetry. Comments, anyone? Thanks Chris Cahill
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