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Lachlan Cranswick (lachlan@melbpc.org.au) wrote: : I'm wondering if someone out there would remember the reference for : (from Memory) a small Chemistry in Britain(?) (8 to 18 months old) : article on Incorrect structures caused bya certain type of false minima. : This was on organo-metalic singlecrystals and this problem was supposedly : well known by a "previous generation" of crystallographers - but forgotten : by people using new generation software(?). I saw a summary of the article in Chemical and Enginerring News. I think it was referring to a JACS article by G. Parkin. The error responsible for the false minima is the "polar dispersion error" (PDE). This comes from neglecting the anomalous dispersion terms in the structure factor calculation when working in polar space groups ( I am away from the office, and don't have references handy, so I don't want to say anything further which may be inadvertently misleading). Happy New Year! Paul -- Paul D. Boyle | boyle@laue.chem.ncsu.edu Director, X-ray Structural Facility | phone: (919) 515-7362 Department of Chemistry - Box 8204 | FAX: (919) 515-5079 North Carolina State University | Raleigh, NC, 27695-8204 http://laue.chem.ncsu.edu/web/xray.welcome.htmlReturn to Top
Paul D. Boyle (boyle@laue.chem.ncsu.edu) wrote: : Lachlan Cranswick (lachlan@melbpc.org.au) wrote: : : I'm wondering if someone out there would remember the reference for : : (from Memory) a small Chemistry in Britain(?) (8 to 18 months old) : : I saw a summary of the article in Chemical and Enginerring News. : I think it was referring to a JACS article by G. Parkin. The error This may help...it is the result of a Dialog search. 3/2/1 DIALOG(R)File 313:CA SEARCH(R) (c) 1996 American Chemical Society. All rts. reserv. 123326167 CA: 123(24)326167y JOURNAL False Minima and the Perils of a Polar Axis in X-ray Structure Solutions: Molecular Structures of W(PMe3)4H2X2 (X = F, Cl, Br) and W(PMe3)4H2F2(H2O) AUTHOR(S): Murphy, Vincent J.; Rabinovich, Daniel; Parkin, Gerard LOCATION: Department of Chemistry, Columbia University, New York, NY, 10027, USA JOURNAL: J. Am. Chem. Soc. DATE: 1995 VOLUME: 117 NUMBER: 38 PAGES: 9762-3 CA275008 Crystallography and Liquid Crystals CA278XXX Inorganic Chemicals and Reactions IDENTIFIERS: mol structure tungsten methylphosphine halo hydrido Best wishes, Jim. -- -- Dr. James V. Silverton jvs@helix.nih.gov 301-496-1515 (OFFICE) 301-402-3404 (FAX) NHLBI/LBC, 10/7N-307, 10 CENTER DR MSC 1676, BETHESDA MD 20892-1676Return to Top