[Ifeffit] FEFF and XANES

[Frommer Jakob]

Dear all,
I have a FEFF related question (I know that this is an IFEFFIT list, but I guess the subjects are closely related). I try to model some of my Cr XANES data with FEFF (following the procedure outlined in an excellent publication in Chem Phys 300 (2004) 13-22 – the authors have shown that it is possible to explain the Cr XANES spectra at least qualitatively by the means of FEFF calculations). I have however still some trouble to understand the difference (or the relation) between the XANES results given in the xmu.dat file and the l-projected density of states results (ldosXX.dat). Due to rho(E)=rho_0(E)[1+chi(E)] I would expect them to conincide (if the rho is calculated for the correct l – i.e. if the matrix element is non-zero). However I observed that the ldos and the xmu do not always coincide – is this possible? Furthermore at the white line position (from what I know, the white line is commonly interpreted as being due to the transition into unoccupied but bound states) the xmu shows strong intensity whereas the ldos do not (maybe one comment: I assume that the e-scales in the ldos-file and in the xmu-file are the same).
I am using FEFF8.2 with the SCF, DOS, XANES and FMS card.
I would be obliged for your help.
Thanks
Jakob

P.s.: for hydroxide structures FEFF is always returning “bad counts” if I include the protons into the FEFF calculation – however this might be also due to bad input structures.


___________________________________________________

Jakob Frommer
Soil Chemistry Group
Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich
Universitätstrasse 16, CHN F19
CH - 8092 Zürich
Tel: +41 44 632 87 58
Fax: +41 44 633 11 18
Email: jakob.frommer at env.ethz.ch
http://www.ito.ethz.ch/SoilChem/