Dear Armel Happy new year. Here is a delayed response for UPP-7 - actually done in November then set aside to be dealt with in the vacation, but unfortunately I have been out of email communication since December due to system changes here. Like your other correspondents, I agree that this alpha-artemether polymorph is orthorhombic. The main feature of interest with this dataset is the need for a substantial 2Theta zero correction of 0.068 +-0.0075 degrees to be added to 2Theta-obs to obtain the corrected values (i.e. a 2theta zero error of -0.068 degrees). Otherwise the problem is quite straightforward and was easily solved by several programs within Crysfire (FJZN6, ITO12, TAUP, etc.). It was then passed to Chekcell in the usual way for refinement and evaluation. The observed lines beyond the 25th are too sparse to be useful, and were omitted from the refinement, which gave the following orthorhombic cell (with esds in brackets): a = 11.1323 (0.0084) b = 13.8259 (0.0082) c = 10.4829 (0.0068) V = 1613.461 The volume is lower than most other solutions submitted as a consequence of allowing for the 2Theta zero error, and hence I think more reliable. The above cell indexes all of the first 25 lines with 63 calc lines, if the spacegroup is taken to be P212121. A centrosymmetric spacegroup of Pmmn would only require 58 calc lines, but was rejected in favour of P212121 on the assumption that a natural product like this would probably be chiral, and P212121 is one of the commonest orthorhombic spacegroups for such materials. With best wishes Robin P.S. My apologies to Crysfire users who have been getting linkfile errors running Crysfire in 2004. This seems to be a bizarre year-related problem, which did not occur in 2002 or 2003!! I'm looking into this and will hopefully be able to release a fix soon - in the meanwhile a sort of workaround is to temporarily set the year back to 2003 for the duration of the Crysfire run. -------------------------------------- To: sdpd@yahoogroups.com From: Armel Le Bail Date: Fri, 09 Jan 2004 09:47:36 +0100 Subject: [sdpd] UPPW-7 Reply-to: sdpd@yahoogroups.com A few hours (5) are remaining for sending your results about the Unindexed Powder Pattern of the Week -7 Armel Yahoo! Groups Links To visit your group on the web, go to: http://groups.yahoo.com/group/sdpd/ To unsubscribe from this group, send an email to: sdpd-unsubscribe@yahoogroups.com Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/ Yahoo! Groups Links To visit your group on the web, go to: http://groups.yahoo.com/group/sdpd/ To unsubscribe from this group, send an email to: sdpd-unsubscribe@yahoogroups.com Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/