Based on the problems people described at the Bayreuth Powder workshop, there is a draft webpage on "Restrained Rietveld Refinement or Organics" presently based around the Laboratory Powder X-ray Tetracycline Hydrochloride data used for the structure solution round robin (SDPDRR): http://www.ccp14.ac.uk/solution/restrained_rietveld/ Using: Crystals for Windows for DLS modelling and generating the bond-length, bond-angle, planar restraints that can be passed onto various Rietveld software that have these options. http://www.ccp14.ac.uk/solution/restrained_rietveld/dlscrystals.html GUI WinORTEP to view the structure as it is refining and routinely obtain bond-lengths and angles (GUI WinORTEP can open Shelx, CIF GSAS, Fullprof, LHPM-Rietica and a variety of other formats) Examples: GSAS (using also the EXPGUI interface) and Fullprof http://www.ccp14.ac.uk/solution/restrained_rietveld/restrain_gsas.html http://www.ccp14.ac.uk/solution/restrained_rietveld/restrain_fullprof.html ----- As there could be errors and dodgy suggestions in the pages, corrections, suggestions and tricks appreciated. Lachlan. PS: A few queries: What are the restraint options available in the various Rietveld programs? GSAS seems to have the option for bond-length - bond-angle - planar and torsion angle restraints. Most other Rietveld programs with restrain options seem limited to just bond-length restraints? My impression is that bond-angle and planar restraints are also very useful in keeping a refinement physically meaningful(?) Are there any Rietveld programs out there that can insert "riding" hydrogen restraints for correct handling of placed hydrogens during the refinement? -- Lachlan M. D. Cranswick Collaborative Computational Project No 14 (CCP14) for Single Crystal and Powder Diffraction Daresbury Laboratory, Warrington, WA4 4AD U.K Tel: +44-1925-603703 Fax: +44-1925-603124 E-mail: [EMAIL PROTECTED] Ext: 3703 Room C14 http://www.ccp14.ac.uk
