[Ifeffit] XANES and DOS calculations

Dear Feff Users, first of all I must admit that I am a total beginner and probably there are some things which I don’t understand very well. I need to make XANES and DOS calculations for K-edge of sulfur and then compare them with experiment. I use feff 8.4. First, I started from inorganic compounds such as CdS. I generated feff.inp file in ATOMS and first run feff with default values (generated by ATOMS). The fit wasn’t perfect so I started to change parameters-FMS and SCF but there was so significant improvement. I can only add that others fit are even worse. My question is which parameter I should change or which card should I add to make XANES calculations better? Maybe you can recommend any paper? The second question is about DOS calculations. I took the pDOS functions for each atom, set Fermi level from ldosNN files, but the main peaks are below this level and I don’t have any correspondence with XANES spectrum. For other compounds I have the same problem. Should I add any extra shift? I will be grateful for your advice. Regards Joanna Czapla I add the original feff.inp file generated by ATOMS: * This feff8 input file was generated by WebAtoms 1.8 (Atoms 3.0beta10) * Atoms written by and copyright (c) Bruce Ravel, 1998-2001 TITLE name: CdS (greenockite) (cubic zinc sulfide structure) TITLE formula: CdS TITLE sites: Cd1,S1 TITLE refer1: wyckoff 1,III,110 TITLE refer2: TITLE schoen: TITLE notes1: cubic zinc sulfide structure * S K edge energy = 2472.0 eV EDGE K S02 1.0 * pot xsph fms paths genfmt ff2chi CONTROL 1 1 1 1 1 1 PRINT 1 0 0 0 0 0 *** ixc=0 means to use Hedin-Lundqvist * ixc [ Vr Vi ] EXCHANGE 0 *** Radius of small cluster for *** self-consistency calculation *** A sphere including 2 shells is *** a good choice *** l_scf = 0 for a solid, 1 for a molecule * r_scf [ l_scf n_scf ca ] SCF 4.0 *** Upper limit of XANES calculation. *** This *must* be uncommented to *** make Feff calculate full multiple *** scattering rather than a path expansion * kmax [ delta_k delta_e ] XANES 4.0 *** Radius of cluster for Full Multiple *** Scattering calculation *** l_fms = 0 for a solid, 1 for a molecule * r_fms l_fms FMS 5.54240 0 *** Energy grid over which to calculate *** DOS functions * emin emax eimag LDOS -30 20 0.1 *** for EXAFS: RMAX 8.0 and uncomment *** the EXAFS card RPATH 0.1 *EXAFS 20 POTENTIALS * ipot Z element l_scmt l_fms stoichiometry 0 16 S 2 2 0.001 1 48 Cd 3 3 4 2 16 S 2 2 4 ATOMS * this list contains 87 atoms * x y z ipot tag distance 0.00000 0.00000 0.00000 0 S1 0.00000 0 -1.45450 1.45450 1.45450 1 Cd1 2.51927 1 1.45450 -1.45450 1.45450 1 Cd1 2.51927 2 1.45450 1.45450 -1.45450 1 Cd1 2.51927 3 -1.45450 -1.45450 -1.45450 1 Cd1 2.51927 4 2.90900 2.90900 0.00000 2 S1 4.11395 5 -2.90900 2.90900 0.00000 2 S1 4.11395 6 2.90900 -2.90900 0.00000 2 S1 4.11395 7 -2.90900 -2.90900 0.00000 2 S1 4.11395 8 2.90900 0.00000 2.90900 2 S1 4.11395 9 -2.90900 0.00000 2.90900 2 S1 4.11395 10 0.00000 2.90900 2.90900 2 S1 4.11395 11 0.00000 -2.90900 2.90900 2 S1 4.11395 12 2.90900 0.00000 -2.90900 2 S1 4.11395 13 -2.90900 0.00000 -2.90900 2 S1 4.11395 14 0.00000 2.90900 -2.90900 2 S1 4.11395 15 0.00000 -2.90900 -2.90900 2 S1 4.11395 16 4.36350 1.45450 1.45450 1 Cd1 4.82403 17 1.45450 4.36350 1.45450 1 Cd1 4.82403 18 -4.36350 -1.45450 1.45450 1 Cd1 4.82403 19 -1.45450 -4.36350 1.45450 1 Cd1 4.82403 20 1.45450 1.45450 4.36350 1 Cd1 4.82403 21 -1.45450 -1.45450 4.36350 1 Cd1 4.82403 22 -4.36350 1.45450 -1.45450 1 Cd1 4.82403 23 -1.45450 4.36350 -1.45450 1 Cd1 4.82403 24 4.36350 -1.45450 -1.45450 1 Cd1 4.82403 25 1.45450 -4.36350 -1.45450 1 Cd1 4.82403 26 -1.45450 1.45450 -4.36350 1 Cd1 4.82403 27 1.45450 -1.45450 -4.36350 1 Cd1 4.82403 28 5.81800 0.00000 0.00000 2 S1 5.81800 29 -5.81800 0.00000 0.00000 2 S1 5.81800 30 0.00000 5.81800 0.00000 2 S1 5.81800 31 0.00000 -5.81800 0.00000 2 S1 5.81800 32 0.00000 0.00000 5.81800 2 S1 5.81800 33 0.00000 0.00000 -5.81800 2 S1 5.81800 34 -4.36350 4.36350 1.45450 1 Cd1 6.34002 35 4.36350 -4.36350 1.45450 1 Cd1 6.34002 36 -4.36350 1.45450 4.36350 1 Cd1 6.34002 37 -1.45450 4.36350 4.36350 1 Cd1 6.34002 38 4.36350 -1.45450 4.36350 1 Cd1 6.34002 39 1.45450 -4.36350 4.36350 1 Cd1 6.34002 40 4.36350 4.36350 -1.45450 1 Cd1 6.34002 41 -4.36350 -4.36350 -1.45450 1 Cd1 6.34002 42 4.36350 1.45450 -4.36350 1 Cd1 6.34002 43 1.45450 4.36350 -4.36350 1 Cd1 6.34002 44 -4.36350 -1.45450 -4.36350 1 Cd1 6.34002 45 -1.45450 -4.36350 -4.36350 1 Cd1 6.34002 46 5.81800 2.90900 2.90900 2 S1 7.12557 47 -5.81800 2.90900 2.90900 2 S1 7.12557 48 2.90900 5.81800 2.90900 2 S1 7.12557 49 -2.90900 5.81800 2.90900 2 S1 7.12557 50 5.81800 -2.90900 2.90900 2 S1 7.12557 51 -5.81800 -2.90900 2.90900 2 S1 7.12557 52 2.90900 -5.81800 2.90900 2 S1 7.12557 53 -2.90900 -5.81800 2.90900 2 S1 7.12557 54 2.90900 2.90900 5.81800 2 S1 7.12557 55 -2.90900 2.90900 5.81800 2 S1 7.12557 56 2.90900 -2.90900 5.81800 2 S1 7.12557 57 -2.90900 -2.90900 5.81800 2 S1 7.12557 58 5.81800 2.90900 -2.90900 2 S1 7.12557 59 -5.81800 2.90900 -2.90900 2 S1 7.12557 60 2.90900 5.81800 -2.90900 2 S1 7.12557 61 -2.90900 5.81800 -2.90900 2 S1 7.12557 62 5.81800 -2.90900 -2.90900 2 S1 7.12557 63 -5.81800 -2.90900 -2.90900 2 S1 7.12557 64 2.90900 -5.81800 -2.90900 2 S1 7.12557 65 -2.90900 -5.81800 -2.90900 2 S1 7.12557 66 2.90900 2.90900 -5.81800 2 S1 7.12557 67 -2.90900 2.90900 -5.81800 2 S1 7.12557 68 2.90900 -2.90900 -5.81800 2 S1 7.12557 69 -2.90900 -2.90900 -5.81800 2 S1 7.12557 70 -7.27250 1.45450 1.45450 1 Cd1 7.55780 71 -1.45450 7.27250 1.45450 1 Cd1 7.55780 72 7.27250 -1.45450 1.45450 1 Cd1 7.55780 73 1.45450 -7.27250 1.45450 1 Cd1 7.55780 74 4.36350 4.36350 4.36350 1 Cd1 7.55780 75 -4.36350 -4.36350 4.36350 1 Cd1 7.55780 76 -1.45450 1.45450 7.27250 1 Cd1 7.55780 77 1.45450 -1.45450 7.27250 1 Cd1 7.55780 78 7.27250 1.45450 -1.45450 1 Cd1 7.55780 79 1.45450 7.27250 -1.45450 1 Cd1 7.55780 80 -7.27250 -1.45450 -1.45450 1 Cd1 7.55780 81 -1.45450 -7.27250 -1.45450 1 Cd1 7.55780 82 -4.36350 4.36350 -4.36350 1 Cd1 7.55780 83 4.36350 -4.36350 -4.36350 1 Cd1 7.55780 84 1.45450 1.45450 -7.27250 1 Cd1 7.55780 85 -1.45450 -1.45450 -7.27250 1 Cd1 7.55780 86 END 2010/5/21 :

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Message: 1 Date: Thu, 20 May 2010 14:14:18 -0700 (PDT) From: mohamed sobhy To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] fitting Message-ID: <725080.73390.qm@web50302.mail.re2.yahoo.com> Content-Type: text/plain; charset="us-ascii"

Dear all thanks for your help and explanation about the background I fitted my data after removing the background and in the attached file I got this fitting, although all the values are good but I think the coordination number should be less than 8 (for the first shell) due to irradiation. So how can I get the right coordination number? How to improve the fitting of second shell? thanks