Re: [Ifeffit] Comparison of "amp" between Feff8.40 and feff6 - Curved waves or Plane waves?
Dear all, While I am calculating FEFF path through Feff8.40 using the "feff8.inp" as attached, I notice that the value of "amp" shown on "FEFF interpretation page" for some paths goes over 100%. For example, path 14 has a Reff=3.9317 far away from first shell, yet it has an "amp"=169.913. On the contrary, if I do the same in Artemis through embedded Feff6.0(using "feff6.inp"), none of paths has an "amp" over 100%. I am guessing this could be all right because Feff8 is using curved waves Feff6 instead plane waves. Any comments on this would be greatly appreciated! Ying Ying Zou Research Assoc., Dr.Phys. Physics Department, UWM =======================feff8.inp======================================= * This feff.inp file generated by ATOMS, version 2.50 * ATOMS written by and copyright (c) Bruce Ravel, 1992-1999 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * total mu = 5194.4 cm^-1, delta mu = 761.6 cm^-1 * specific gravity = 7.942, cluster contains 25 atoms. * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * mcmaster corrections: 0.00093 ang^2 and 0.165E-05 ang^4 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * TITLE Perovskite: PbTiO3 EDGE K S02 1.0 * pot xsph fms paths genfmt ff2chi CONTROL 1 1 1 1 1 1 PRINT 1 0 0 0 0 3 * r_scf [ l_scf n_scf ca ] SCF 3.88586 0 15 0.1 * ixc [ Vr Vi ] EXCHANGE 0 0 0 EXAFS RPATH 7.77172 * kmax [ delta_k delta_e ] *XANES 4.0 0.07 0.5 * r_fms [ l_fms ] *FMS 3.88586 ******** * *RPATH 0.10000 * emin emax resolution *LDOS -20 20 0.1 POTENTIALS * ipot z [ label l_scmt l_fms stoichiometry ] 0 22 Ti -1 -1 0 1 8 O -1 -1 3 2 82 Pb -1 -1 1 3 22 Ti -1 -1 1 ATOMS 0.00000 0.00000 0.00000 0 Ti 0.00000 0.00000 0.00000 -1.76630 1 Oapical 1.76630 1.95250 0.00000 0.32417 1 Oplanar 1.97923 0.00000 -1.95250 0.32417 1 Oplanar 1.97923 -1.95250 0.00000 0.32417 1 Oplanar 1.97923 0.00000 1.95250 0.32417 1 Oplanar 1.97923 0.00000 0.00000 2.38970 1 Oapical 2.38970 -1.95250 -1.95250 1.91592 2 Pb 3.36084 1.95250 -1.95250 1.91592 2 Pb 3.36084 -1.95250 1.95250 1.91592 2 Pb 3.36084 1.95250 1.95250 1.91592 2 Pb 3.36084 1.95250 -1.95250 -2.24008 2 Pb 3.55563 -1.95250 1.95250 -2.24008 2 Pb 3.55563 -1.95250 -1.95250 -2.24008 2 Pb 3.55563 1.95250 1.95250 -2.24008 2 Pb 3.55563 -3.90500 0.00000 0.00000 3 Ti 3.90500 0.00000 3.90500 0.00000 3 Ti 3.90500 3.90500 0.00000 0.00000 3 Ti 3.90500 0.00000 -3.90500 0.00000 3 Ti 3.90500 0.00000 0.00000 4.15600 3 Ti 4.15600 0.00000 0.00000 -4.15600 3 Ti 4.15600 3.90500 0.00000 -1.76630 1 Oapical 4.28589 0.00000 -3.90500 -1.76630 1 Oapical 4.28589 -3.90500 0.00000 -1.76630 1 Oapical 4.28589 0.00000 3.90500 -1.76630 1 Oapical 4.28589 END ============================================================================ ========================feff6.inp========================================== * This feff6 input file was generated by Artemis 0.8.011 * Atoms written by and copyright (c) Bruce Ravel, 1998-2001 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * total mu*x=1: 2.06 microns, unit edge step: 13.38 microns * specific gravity = 7.942 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * Normalization correction: 0.00048 ang^2 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * ----------------------------------------------------------------- * The following crystallographic data were used: * * title Pb Ti O3 * title Glazer A M * title # Powder profile refinement of lead zirconate titanate at several temperatures. * title # II. Pure PbTiO3 * title # Locality: synthetic * title # Sample: T = 25 C * space = P 4 m m * a = 3.9050 b = 3.9050 c = 4.1560 * alpha = 90.0 beta = 90.0 gamma = 90.0 * core = Ti edge = K * atoms * ! elem x y z tag occ * Pb 0.00000 0.00000 0.00000 Pb 1.00000 * Ti 0.50000 0.50000 0.53900 Ti 1.00000 * O 0.50000 0.50000 0.11400 Oapical 1.00000 * O 0.50000 0.00000 0.61700 Oplanar 1.00000 * ----------------------------------------------------------------- TITLE Pb Ti O3 TITLE Glazer A M TITLE # Powder profile refinement of lead zirconate titanate at several temperatures. TITLE # II. Pure PbTiO3 TITLE # Locality: synthetic TITLE # Sample: T = 25 C HOLE 1 1.0 * Ti K edge (4966.0 eV), second number is S0^2 * mphase,mpath,mfeff,mchi CONTROL 1 1 1 1 PRINT 1 0 0 0 RMAX 4.29550 *CRITERIA curved plane *DEBYE temp debye-temp NLEG 4 POTENTIALS * ipot Z element 0 22 Ti 1 82 Pb 2 22 Ti 3 8 O ATOMS * this list contains 25 atoms * x y z ipot tag distance 0.00000 0.00000 0.00000 0 Ti 0.00000 0.00000 0.00000 -1.76630 3 Oapical_1 1.76630 1.95250 0.00000 0.32417 3 Oplanar_1 1.97923 -1.95250 0.00000 0.32417 3 Oplanar_1 1.97923 0.00000 1.95250 0.32417 3 Oplanar_1 1.97923 0.00000 -1.95250 0.32417 3 Oplanar_1 1.97923 0.00000 0.00000 2.38970 3 Oapical_2 2.38970 1.95250 1.95250 1.91592 1 Pb_1 3.36084 -1.95250 1.95250 1.91592 1 Pb_1 3.36084 1.95250 -1.95250 1.91592 1 Pb_1 3.36084 -1.95250 -1.95250 1.91592 1 Pb_1 3.36084 1.95250 1.95250 -2.24008 1 Pb_2 3.55563 -1.95250 1.95250 -2.24008 1 Pb_2 3.55563 1.95250 -1.95250 -2.24008 1 Pb_2 3.55563 -1.95250 -1.95250 -2.24008 1 Pb_2 3.55563 3.90500 0.00000 0.00000 2 Ti_1 3.90500 -3.90500 0.00000 0.00000 2 Ti_1 3.90500 0.00000 3.90500 0.00000 2 Ti_1 3.90500 0.00000 -3.90500 0.00000 2 Ti_1 3.90500 0.00000 0.00000 4.15600 2 Ti_2 4.15600 0.00000 0.00000 -4.15600 2 Ti_2 4.15600 3.90500 0.00000 -1.76630 3 Oapical_3 4.28589 -3.90500 0.00000 -1.76630 3 Oapical_3 4.28589 0.00000 3.90500 -1.76630 3 Oapical_3 4.28589 0.00000 -3.90500 -1.76630 3 Oapical_3 4.28589 END ========================================================================
On Thursday 28 August 2008 18:42:12 Ying Zou wrote:
While I am calculating FEFF path through Feff8.40 using the "feff8.inp" as attached, I notice that the value of "amp" shown on "FEFF interpretation page" for some paths goes over 100%. For example, path 14 has a Reff=3.9317 far away from first shell, yet it has an "amp"=169.913. On the contrary, if I do the same in Artemis through embedded Feff6.0(using "feff6.inp"), none of paths has an "amp" over 100%. I am guessing this could be all right because Feff8 is using curved waves Feff6 instead plane waves. Any comments on this would be greatly appreciated!
Ying, Two things: 1. Both Feff6 and Feff8 are a curved wave calculations 2. From the Feff6 document (the definition is unchanged in Feff8, to the best of my knowledge, although this definition is not included in the Feff8 document): The curved wave importance ratios are the importance of a particular path relative to the most important path encountered so far in the calculation. If the first path is the most important in the problem, all the importance factors will be expressed as a fraction of that path. However, if the third path considered is the most important, and the first path is the next most important, path 1 will have a factor of 100%, path 2 will be a fraction of the first path's importance, path 3 will have an importance of 100% (since it is now the most important path), and subsequent paths will be expressed as a percent of path 3's importance. So, an amp of 170 for path 14 must be a bug in Feff8. By its own definition, 100 is the largest possible value. I suspect that if you compare that path from the two Feff calculations, they will, in fact, be quite similar. 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/
Ying and Bruce, Some versions of FEFF, at least, do allow amps above 100. They assign 100 to the first path, and then scale from there. The nearest neighbor path in your list is a single oxygen. I didn't run atoms on your input file, but I bet your path 14 is some combination of high degeneracy, focused, and involving the lead. Despite being further, it is more prominent, and thus correctly assigned a higher amp. It may be that this is true for only some versions of FEFF. I've certainly seen it frequently, although I haven't paid attention to whether it's version or even platform dependent. Personally, despite being documented, I would describe the behavior that Bruce describes, where the meaning of amp gets rescaled if a more prominent path is encountered, as a "known bug," while the behavior where amps greater than 100 assigned as more ideal. In any case, this is just cosmetic; it shouldn't affect the feff path itself. --Scott Calvin Sarah Lawrence College On Aug 29, 2008, at 9:32 AM, Bruce Ravel wrote:
On Thursday 28 August 2008 18:42:12 Ying Zou wrote:
While I am calculating FEFF path through Feff8.40 using the "feff8.inp" as attached, I notice that the value of "amp" shown on "FEFF interpretation page" for some paths goes over 100%. For example, path 14 has a Reff=3.9317 far away from first shell, yet it has an "amp"=169.913. On the contrary, if I do the same in Artemis through embedded Feff6.0(using "feff6.inp"), none of paths has an "amp" over 100%. I am guessing this could be all right because Feff8 is using curved waves Feff6 instead plane waves. Any comments on this would be greatly appreciated!
Ying,
Two things:
1. Both Feff6 and Feff8 are a curved wave calculations
2. From the Feff6 document (the definition is unchanged in Feff8, to the best of my knowledge, although this definition is not included in the Feff8 document):
The curved wave importance ratios are the importance of a particular path relative to the most important path encountered so far in the calculation. If the first path is the most important in the problem, all the importance factors will be expressed as a fraction of that path. However, if the third path considered is the most important, and the first path is the next most important, path 1 will have a factor of 100%, path 2 will be a fraction of the first path's importance, path 3 will have an importance of 100% (since it is now the most important path), and subsequent paths will be expressed as a percent of path 3's importance.
So, an amp of 170 for path 14 must be a bug in Feff8. By its own definition, 100 is the largest possible value.
I suspect that if you compare that path from the two Feff calculations, they will, in fact, be quite similar.
B
By looking at the FEFF.inp file it appears that the path in question is a Ti-O-Ti where the angle of this linkage is very close to 180 degree (had it been 180 degree, the total length would be not 3.9317 but either 3.90500 or 4.15600. In a perovskite with Ti on center such angle would be 180 degree but in your input file you have TiO6 octahedron displaced relative to the Pb corners in 100 direction (also known as tetragonal distortion). Still, the angle is close to 180 degree which makes a contribution of forward scattering, triple-scattering paths that go through O in forward direction twice, the strongest - and that should explain why your path amplitude increased over 100 percent. Why the two programs give different amplitude, must be a bug, as Bruce and Scott explained. Anatoly -----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov]On Behalf Of Ying Zou Sent: Thursday, August 28, 2008 6:42 PM To: ifeffit Subject: Re: [Ifeffit] Comparison of "amp" between Feff8.40 and feff6 - Curved waves or Plane waves? Dear all, While I am calculating FEFF path through Feff8.40 using the "feff8.inp" as attached, I notice that the value of "amp" shown on "FEFF interpretation page" for some paths goes over 100%. For example, path 14 has a Reff=3.9317 far away from first shell, yet it has an "amp"=169.913. On the contrary, if I do the same in Artemis through embedded Feff6.0(using "feff6.inp"), none of paths has an "amp" over 100%. I am guessing this could be all right because Feff8 is using curved waves Feff6 instead plane waves. Any comments on this would be greatly appreciated! Ying Ying Zou Research Assoc., Dr.Phys. Physics Department, UWM =======================feff8.inp======================================= * This feff.inp file generated by ATOMS, version 2.50 * ATOMS written by and copyright (c) Bruce Ravel, 1992-1999 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * total mu = 5194.4 cm^-1, delta mu = 761.6 cm^-1 * specific gravity = 7.942, cluster contains 25 atoms. * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * mcmaster corrections: 0.00093 ang^2 and 0.165E-05 ang^4 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * TITLE Perovskite: PbTiO3 EDGE K S02 1.0 * pot xsph fms paths genfmt ff2chi CONTROL 1 1 1 1 1 1 PRINT 1 0 0 0 0 3 * r_scf [ l_scf n_scf ca ] SCF 3.88586 0 15 0.1 * ixc [ Vr Vi ] EXCHANGE 0 0 0 EXAFS RPATH 7.77172 * kmax [ delta_k delta_e ] *XANES 4.0 0.07 0.5 * r_fms [ l_fms ] *FMS 3.88586 ******** * *RPATH 0.10000 * emin emax resolution *LDOS -20 20 0.1 POTENTIALS * ipot z [ label l_scmt l_fms stoichiometry ] 0 22 Ti -1 -1 0 1 8 O -1 -1 3 2 82 Pb -1 -1 1 3 22 Ti -1 -1 1 ATOMS 0.00000 0.00000 0.00000 0 Ti 0.00000 0.00000 0.00000 -1.76630 1 Oapical 1.76630 1.95250 0.00000 0.32417 1 Oplanar 1.97923 0.00000 -1.95250 0.32417 1 Oplanar 1.97923 -1.95250 0.00000 0.32417 1 Oplanar 1.97923 0.00000 1.95250 0.32417 1 Oplanar 1.97923 0.00000 0.00000 2.38970 1 Oapical 2.38970 -1.95250 -1.95250 1.91592 2 Pb 3.36084 1.95250 -1.95250 1.91592 2 Pb 3.36084 -1.95250 1.95250 1.91592 2 Pb 3.36084 1.95250 1.95250 1.91592 2 Pb 3.36084 1.95250 -1.95250 -2.24008 2 Pb 3.55563 -1.95250 1.95250 -2.24008 2 Pb 3.55563 -1.95250 -1.95250 -2.24008 2 Pb 3.55563 1.95250 1.95250 -2.24008 2 Pb 3.55563 -3.90500 0.00000 0.00000 3 Ti 3.90500 0.00000 3.90500 0.00000 3 Ti 3.90500 3.90500 0.00000 0.00000 3 Ti 3.90500 0.00000 -3.90500 0.00000 3 Ti 3.90500 0.00000 0.00000 4.15600 3 Ti 4.15600 0.00000 0.00000 -4.15600 3 Ti 4.15600 3.90500 0.00000 -1.76630 1 Oapical 4.28589 0.00000 -3.90500 -1.76630 1 Oapical 4.28589 -3.90500 0.00000 -1.76630 1 Oapical 4.28589 0.00000 3.90500 -1.76630 1 Oapical 4.28589 END ============================================================================ ========================feff6.inp========================================== * This feff6 input file was generated by Artemis 0.8.011 * Atoms written by and copyright (c) Bruce Ravel, 1998-2001 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * total mu*x=1: 2.06 microns, unit edge step: 13.38 microns * specific gravity = 7.942 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * Normalization correction: 0.00048 ang^2 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * ----------------------------------------------------------------- * The following crystallographic data were used: * * title Pb Ti O3 * title Glazer A M * title # Powder profile refinement of lead zirconate titanate at several temperatures. * title # II. Pure PbTiO3 * title # Locality: synthetic * title # Sample: T = 25 C * space = P 4 m m * a = 3.9050 b = 3.9050 c = 4.1560 * alpha = 90.0 beta = 90.0 gamma = 90.0 * core = Ti edge = K * atoms * ! elem x y z tag occ * Pb 0.00000 0.00000 0.00000 Pb 1.00000 * Ti 0.50000 0.50000 0.53900 Ti 1.00000 * O 0.50000 0.50000 0.11400 Oapical 1.00000 * O 0.50000 0.00000 0.61700 Oplanar 1.00000 * ----------------------------------------------------------------- TITLE Pb Ti O3 TITLE Glazer A M TITLE # Powder profile refinement of lead zirconate titanate at several temperatures. TITLE # II. Pure PbTiO3 TITLE # Locality: synthetic TITLE # Sample: T = 25 C HOLE 1 1.0 * Ti K edge (4966.0 eV), second number is S0^2 * mphase,mpath,mfeff,mchi CONTROL 1 1 1 1 PRINT 1 0 0 0 RMAX 4.29550 *CRITERIA curved plane *DEBYE temp debye-temp NLEG 4 POTENTIALS * ipot Z element 0 22 Ti 1 82 Pb 2 22 Ti 3 8 O ATOMS * this list contains 25 atoms * x y z ipot tag distance 0.00000 0.00000 0.00000 0 Ti 0.00000 0.00000 0.00000 -1.76630 3 Oapical_1 1.76630 1.95250 0.00000 0.32417 3 Oplanar_1 1.97923 -1.95250 0.00000 0.32417 3 Oplanar_1 1.97923 0.00000 1.95250 0.32417 3 Oplanar_1 1.97923 0.00000 -1.95250 0.32417 3 Oplanar_1 1.97923 0.00000 0.00000 2.38970 3 Oapical_2 2.38970 1.95250 1.95250 1.91592 1 Pb_1 3.36084 -1.95250 1.95250 1.91592 1 Pb_1 3.36084 1.95250 -1.95250 1.91592 1 Pb_1 3.36084 -1.95250 -1.95250 1.91592 1 Pb_1 3.36084 1.95250 1.95250 -2.24008 1 Pb_2 3.55563 -1.95250 1.95250 -2.24008 1 Pb_2 3.55563 1.95250 -1.95250 -2.24008 1 Pb_2 3.55563 -1.95250 -1.95250 -2.24008 1 Pb_2 3.55563 3.90500 0.00000 0.00000 2 Ti_1 3.90500 -3.90500 0.00000 0.00000 2 Ti_1 3.90500 0.00000 3.90500 0.00000 2 Ti_1 3.90500 0.00000 -3.90500 0.00000 2 Ti_1 3.90500 0.00000 0.00000 4.15600 2 Ti_2 4.15600 0.00000 0.00000 -4.15600 2 Ti_2 4.15600 3.90500 0.00000 -1.76630 3 Oapical_3 4.28589 -3.90500 0.00000 -1.76630 3 Oapical_3 4.28589 0.00000 3.90500 -1.76630 3 Oapical_3 4.28589 0.00000 -3.90500 -1.76630 3 Oapical_3 4.28589 END ======================================================================== _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
participants (4)
-
Bruce Ravel -
Frenkel, Anatoly -
Scott Calvin -
Ying Zou