Hi Jakob,
As you have noted the fine structure in the projected DOS and the XAS
is the same, so the relation between them is:
XAS = gamma(E) LDOS, where gamma(E) = mu_0(E)/rho_0(E),
where gamma(E) is a smoothly varying atomic-like quantity which
is essentially a ratio of embedded atomic matrix elements. In systems with
a white line $mu_0$ and hence, gamma(E) will likely be peaked at threshold.
As a result the XAS is smoothly related to the LDOS with appropriate
selection rules. This discussion assumes core-hole effects are small,
and final state broadening is applied both the the LDOS and XAS.
J. Rehr
On Mon, 11 Dec 2006, Frommer Jakob wrote:
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 Z?rich
Universit?tstrasse 16, CHN F19
CH - 8092 Z?rich
Tel: +41 44 632 87 58
Fax: +41 44 633 11 18
Email: [EMAIL PROTECTED]
http://www.ito.ethz.ch/SoilChem/
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