fitting simultaneously two different K-edges
Dear friends, Sam Webb, Bruce Ravel or any other, I have XAFS measurements, performed at SSRL at room temperature, of three compounds. All compounds have multielemental character and I have K-edge XAFS of two elements in each compound. It is desirable to make IFEFFIT fitting of both edges simultaneously. In all cases random solution of competing elements is assumed, but there are ferroelectricity, superconductivity or magnetic behaviors that are desirable to be explained. In each case, XAFS would confirm or reject the random character of the solution. I am not such an expert for resolving by myself how to fit together two edges using Artemis software. I'll present each case in the following: 1. rutheno-cuprate (Ru1-xNbx)Sr2Eu1.4 Ce0.6Cu2O10+δ compounds series was studied in both Ru and Nb K-edges. Changes in interatomic distances that could be obtained by EXAFS would tell something about oxygen octahedra around Ru and Nb. 2. g-Fe1-xCrxO3 maghemite for x=0.25, 0.5 and 0.75 was investigated by XAFS in both Fe and Cr K-edges. Possible distortion of oxygen octahedra around both Fe(III) and Cr(III) cations would tell something about not confirmed ferroelectricity. 3. LaFeNiTiO3 has been confirmed to display magnetic behavior and was studied by its Fe and Ti K-edges. Interatomic distances that could be obtained by EXAFS are interesting for checking possible preferential occupation of sites by Fe or Ti atoms. Would any of you, please, suggest how to use Artemis or Sixpack for solving these problems? Sincerely yours -- María Elena Dra. María Elena Montero Cabrera Departamento de Medio Ambiente y Energía Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31109, Chih. México Tel (614) 4391123
Maria Elena, This paper by Scott Calvin is a good place to start nderstanding multiple data set fitting: S. Calvin, et al., Phys Rev B, 66:22, (2002) p. 224405 It is, of course, on a rather different system from the ones you mention below, but the ideas are excellent and well explained. The concepts should be transferable to your measurements. B On Saturday 01 May 2010 12:53:44 pm María Elena Montero Cabrera wrote:
Dear friends, Sam Webb, Bruce Ravel or any other,
I have XAFS measurements, performed at SSRL at room temperature, of three compounds. All compounds have multielemental character and I have K-edge XAFS of two elements in each compound. It is desirable to make IFEFFIT fitting of both edges simultaneously. In all cases random solution of competing elements is assumed, but there are ferroelectricity, superconductivity or magnetic behaviors that are desirable to be explained. In each case, XAFS would confirm or reject the random character of the solution. I am not such an expert for resolving by myself how to fit together two edges using Artemis software. I'll present each case in the following:
1. rutheno-cuprate (Ru1-xNbx)Sr2Eu1.4 Ce0.6Cu2O10+δ compounds series was studied in both Ru and Nb K-edges. Changes in interatomic distances that could be obtained by EXAFS would tell something about oxygen octahedra around Ru and Nb.
2. g-Fe1-xCrxO3 maghemite for x=0.25, 0.5 and 0.75 was investigated by XAFS in both Fe and Cr K-edges. Possible distortion of oxygen octahedra around both Fe(III) and Cr(III) cations would tell something about not confirmed ferroelectricity.
3. LaFeNiTiO3 has been confirmed to display magnetic behavior and was studied by its Fe and Ti K-edges. Interatomic distances that could be obtained by EXAFS are interesting for checking possible preferential occupation of sites by Fe or Ti atoms.
Would any of you, please, suggest how to use Artemis or Sixpack for solving these problems? Sincerely yours
-- 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/
Dear Maria,
If you haven't already done so, I would suggest that you begin by
separately fitting the data for each edge on each sample. This will
give you a good understanding of the local structure around each metal
ion. Once you have this intimacy with the structural models, you
will be able to tell what might be constrained between the two
different metal atoms. Once you get to that point, getting the
software to combine the fits will not seem very hard ;).
--Matt
2010/5/1 María Elena Montero Cabrera
Dear friends, Sam Webb, Bruce Ravel or any other,
I have XAFS measurements, performed at SSRL at room temperature, of three compounds. All compounds have multielemental character and I have K-edge XAFS of two elements in each compound. It is desirable to make IFEFFIT fitting of both edges simultaneously. In all cases random solution of competing elements is assumed, but there are ferroelectricity, superconductivity or magnetic behaviors that are desirable to be explained. In each case, XAFS would confirm or reject the random character of the solution. I am not such an expert for resolving by myself how to fit together two edges using Artemis software. I'll present each case in the following:
1. rutheno-cuprate (Ru1-xNbx)Sr2Eu1.4 Ce0.6Cu2O10+δ compounds series was studied in both Ru and Nb K-edges. Changes in interatomic distances that could be obtained by EXAFS would tell something about oxygen octahedra around Ru and Nb.
2. g-Fe1-xCrxO3 maghemite for x=0.25, 0.5 and 0.75 was investigated by XAFS in both Fe and Cr K-edges. Possible distortion of oxygen octahedra around both Fe(III) and Cr(III) cations would tell something about not confirmed ferroelectricity.
3. LaFeNiTiO3 has been confirmed to display magnetic behavior and was studied by its Fe and Ti K-edges. Interatomic distances that could be obtained by EXAFS are interesting for checking possible preferential occupation of sites by Fe or Ti atoms.
Would any of you, please, suggest how to use Artemis or Sixpack for solving these problems?
Sincerely yours
-- María Elena
Dra. María Elena Montero Cabrera Departamento de Medio Ambiente y Energía Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31109, Chih. México Tel (614) 4391123
_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
participants (3)
-
Bruce Ravel -
María Elena Montero Cabrera -
Matt Newville