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INTRODUCTION The results from a third structure determination

The third Structure Determination by Powder Diffractometry Round Robin (SDPDRR-3) L.M.D. Cranswick and A. Le Bail Canadian Neutron Beam Centre, National Research Council Canada, Building 459, Chalk River Laboratories, Chalk River ON, Canada, K0J 1J0. Email : lachlan.cranswick@nrc.gc.ca

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INTRODUCTION The results from a third structure determination

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  1. The third Structure Determination by Powder Diffractometry Round Robin (SDPDRR-3) L.M.D. Cranswick and A. Le Bail Canadian Neutron Beam Centre, National Research Council Canada, Building 459, Chalk River Laboratories, Chalk River ON, Canada, K0J 1J0. Email : lachlan.cranswick@nrc.gc.ca Université du Maine, Laboratoire des Oxydes et Fluorures, CNRS UMR 6010, Av. O. Messiaen, 72085 Le Mans, France. Email : Armel.Le_Bail@univ-lemans.fr INTRODUCTION The results from a third structure determination by powder diffractometry (SDPD) round-robin are summarized. From the 175 potential participants having downloaded the powder data, 9 have sent a total of 12 solutions (8 and 4 respectively for samples 1 and 2, a calcium tartrate tetrahydrated and a lanthanum tungstate). They used 7 different computer programs for structure solution (ESPOIR, EXPO, FOX, PSSP, SHELXS, SUPERFLIP, TOPAS),applying either the Patterson or direct methods, direct space methods, or the charge flipping approach. Sample 1 : CaC4H4O6.4H2O Conventional X-rays Sample 2 : La18W10O57 Synchrotron Neutron CONCLUSION Solving a structure from powder data remains a hard job, an order of magnitude harder than solving a problem with similar complexity from single crystal data. Nevertheless, a few more steps in the direction of routine were accomplished since the two previous round-robins : that time, not only the computer program developers were successful, but also some more standard users. No result was obtained from crystal structure prediction experts. • REFERENCES • Adil, K., Le Bail, A., Dujardin, G. & Maisonneuve V. (2007). Polyhedron 26, 2493- 2497. • Chambrier M.H., Le Bail A. & Goutenoire F. (2008). http://www.crystallography.net/ • Clegg, W. & Teat, S.J. (2000). Acta Cryst. C56, 1343-1345. • Le Bail A. (2003). COD1000005 - http://www.crystallography.net/ • Le Bail, A. & Cranswick, L.M.D. (2001). Commission on Powder Diffraction IUCr Newsletter 25, 7-9. • Le Bail, A. & Cranswick, L.M.D. (2003). Commission on Powder Diffraction IUCr Newsletter 29, 31-34. • Le Bail, A., Bazin, D., Daudon, M. & Maisonneuve, V. (2008). http://www.crystallography.net/ • Zhu, J.H., Wu, H.X. & Le Bail, A. (1999). Solid State Science, 1, 55-62.

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