Bond length determination EXAFS vs XRD
Happy Thanksgiving All! Can someone, send me some references which explains some of the reasons why the bond lengths fitted in EXAFS would be different from that fitted in XRD (assuming that we implemented the crystal model predicted by XRD correctly in Artemis)? I would really appreciate this! Sincerely -- Joseph Washington Research Assistant Department of Physics North Carolina State University 431 Riddick Hall Raleigh, NC 27695-8202 email: jswashin@ncsu.edu
XRD measures interplanar spacing, and XAFS - interatomic distances, and they are not the same if disorder is present. Look for articles by Boyce and Mikkelsen, Jr., in Phys Rev B in 1980's who were the first discussing these concepts in GaAs-InAs semiconductors and also KBr-RbBr ionic salts. They showed that the average structure ascertained by diffraction differs from the local structure measured by EXAFS. Modern day high energy XRD/PDF measures interatomic distances more accurately than Bragg peak analysis can do but how accurately it agrees with EXAFS is still subject of debates. Anatoly ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of Joseph Washington Sent: Fri 11/27/2009 2:08 PM To: XAFS Analysis using Ifeffit Subject: [Ifeffit] Bond length determination EXAFS vs XRD Happy Thanksgiving All! Can someone, send me some references which explains some of the reasons why the bond lengths fitted in EXAFS would be different from that fitted in XRD (assuming that we implemented the crystal model predicted by XRD correctly in Artemis)? I would really appreciate this! Sincerely -- Joseph Washington Research Assistant Department of Physics North Carolina State University 431 Riddick Hall Raleigh, NC 27695-8202 email: jswashin@ncsu.edu _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
I would like to request a .cif file for the alpha & beta Nickel hydroxide. If someone also have .cif files for Cobalt hydroxide this will be greatly appreciated. Is there a single crystal data base for .cif files? thanks, Scott A. Wicker Sr. Ph.d Graduate Student Environmental Toxicology Southern University A & M Baton Rouge, LA 70813 School: scott_wicker_00@cxs.subr.edu Home: swicker@cox.net -----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of Frenkel, Anatoly Sent: Fri 11/27/2009 1:12 PM To: jswashin@ncsu.edu; XAFS Analysis using Ifeffit Subject: RE: [Ifeffit] Bond length determination EXAFS vs XRD XRD measures interplanar spacing, and XAFS - interatomic distances, and they are not the same if disorder is present. Look for articles by Boyce and Mikkelsen, Jr., in Phys Rev B in 1980's who were the first discussing these concepts in GaAs-InAs semiconductors and also KBr-RbBr ionic salts. They showed that the average structure ascertained by diffraction differs from the local structure measured by EXAFS. Modern day high energy XRD/PDF measures interatomic distances more accurately than Bragg peak analysis can do but how accurately it agrees with EXAFS is still subject of debates. Anatoly _____ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of Joseph Washington Sent: Fri 11/27/2009 2:08 PM To: XAFS Analysis using Ifeffit Subject: [Ifeffit] Bond length determination EXAFS vs XRD Happy Thanksgiving All! Can someone, send me some references which explains some of the reasons why the bond lengths fitted in EXAFS would be different from that fitted in XRD (assuming that we implemented the crystal model predicted by XRD correctly in Artemis)? I would really appreciate this! Sincerely -- Joseph Washington Research Assistant Department of Physics North Carolina State University 431 Riddick Hall Raleigh, NC 27695-8202 email: jswashin@ncsu.edu _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
On Sunday 29 November 2009 01:06:19 pm Scott Wicker (Student) wrote:
I would like to request a .cif file for the alpha & beta Nickel hydroxide. If someone also have .cif files for Cobalt hydroxide this will be greatly appreciated. Is there a single crystal data base for .cif files?
See the second question at http://cars9.uchicago.edu/ifeffit/FAQ/RunningFeff B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 My homepage: http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/
participants (4)
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Bruce Ravel -
Frenkel, Anatoly -
Joseph Washington -
Scott Wicker (Student)