Dear Armel, >From the comparison of your distances and angles with the single-crystal ones, >two obvious conclusions can be drawn: 1) Applying a simplified refinement model one can't expect accurate results 2) Uncertainty estimations in Rietveld programs are inadequately optimistic
Here you may see unrestrained DDM results for this structure: http://sites.google.com/site/ddmsuite/tutorials/bethcl-DDM.cif http://sites.google.com/site/ddmsuite/tutorials/bethcl-DDM.png I used synchrotron data (10-years old) from: http://sdpd.univ-lemans.fr/uppw/bethanechol.zip The main problem was in a complex anisotropic and asymmetric peak broadening that you mentioned in your publication. I modeled it by including two pseudo-phases with variable lattice parameters. The resulted distances and angles agree with the single-crystal ones within 3 e.s.u.: Single-crystal DDM C2 O4 1.359(4) 1.356(9) O4 C5 1.454(4) 1.473(7) O1 C2 1.217(4) 1.200(11) C2 N3 1.338(5) 1.331(10) C5 C6 1.521(5) 1.518(7) C5 C7 1.522(5) 1.530(8) C7 N8 1.516(4) 1.534(7) N8 C9 1.501(5) 1.512(7) N8 C10 1.496(4) 1.495(8) N8 C11 1.499(5) 1.491(8) C2 O4 C5 116.6(3) 116.5(5) O1 C2 O4 123.4(3) 123.5(7) O1 C2 N3 125.4(3) 127.2(7) N3 C2 O4 111.1(3) 109.3(7) O4 C5 C6 108.1(3) 107.2(5) O4 C5 C7 110.2(3) 109.3(5) C6 C5 C7 109.3(3) 108.0(4) N8 C7 C5 117.6(3) 117.1(4) C9 N8 C7 107.3(3) 107.6(4) C10 N8 C7 111.8(3) 110.8(5) C11 N8 C7 112.1(3) 112.6(4) C10 N8 C9 108.1(3) 107.8(4) C11 N8 C9 107.3(3) 108.9(4) C10 N8 C11 110.0(3) 109.0(4) The C-C precision is 0.0075 A, reasonably comparable to the single-crystal 0.005 A. The results can be further improved if the available XRD pattern is not interrupted at 26.8 degrees and/or if the sample is better prepared. So, the unrestrained SDPD future exists and it is much more interesting. Best regards, Leonid ******************************************************* Leonid A. Solovyov Institute of Chemistry and Chemical Technology 660049, K. Marx 42, Krasnoyarsk, Russia http://sites.google.com/site/solovyovleonid ******************************************************* ________________________________ From: Armel Le Bail <armel.le_b...@univ-lemans.fr> To: s...@yahoogroups.com Sent: Tuesday, September 3, 2013 3:53 PM Subject: [sdpd] Bethanechol chloride : new single crystal results Hi, For those especially interested in comparing unrestrained SDPD results with single crystal ones a new example is available, BC (bethanechol chloride) which was one of the 2003 UPPWs "Unindexed Powder Pattern of the Week" : http://sdpd.univ-lemans.fr/uppw/index.html UPPW-11 : http://sdpd.univ-lemans.fr/uppw/uppw11.html It was extensively used for testing various indexing sofware and proposed for benchmarking (2004) : http://www.degruyter.com/view/j/zkri.2004.219.issue-12-2004/zkri.219.12.783.55862/zkri.219.12.783.55862.xml;jsessionid=5297B32E4713E27A7B5A9DAB82D2ACE6 http://sdpd.univ-lemans.fr/uppw/benchmarks/ SDPD published in 2010, restraints on H only, 298 K : http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8481214 Single crystals finally synthesized, structure published in 2013 (123 K) : http://pubs.rsc.org/en/Content/ArticleLanding/2013/CE/c3ce40707a Results said to be "in agreement". Best, Armel Le Bail __._,_.___ Reply via web post Reply to sender Reply to group Start a New Topic Messages in this topic (1) Recent Activity: Visit Your Group Switch to: Text-Only, Daily Digest • Unsubscribe • Terms of Use • Send us Feedback . __,_._,___
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
