[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: E0 value assumed in RHOLNN.DAT files
On Tuesday 03 August 2004 10:58 am, ALNemir@aol.com wrote:
> I am employing FEFF8 to do XANES calculations, using SCF and LDOS cards
> among others. The rholnn.dat files are output files of the LDOS card and
> are supposed to be instrumental in examining densities of states for
> interpreting XANES. When rholnn.dat files are plotted it appears that the
> horizontal axis is in units of eV and with respect to E0. In order to
> change that to the absolute energies, and to be able to plot rholnn.dat
> files against the XANES cardâ??s output file, xmu.dat, I need to know what
> E0 is with respect to which the rholnn.dat files are written. I was
> wondering where I can find that value of E0. Please correct me if I am
> wrong, but I am assuming that this E0 is calculated during the SCF
> calculation.
The Fermi energy, on the energy scale given by the first column of
data, is given in the first line of the rholNN.dat file. That is the
edge energy of the XANES measurement. Whetever the value for e0 in
the measurement for which you ran the calculation, that is the
absolute energy value which corresponds to the the Fermi energy.
> Also, I was wondering what the rhocnn.dat files can be used for, since they
> are not mentioned in the FEFF8 manual.
The rhocNN.dat files are the densities of the overlapped atoms. The
self-consistency redistributes charge, resulting the differences
between rhocNN and rholNN. Another way of stating this is that there
is an equation for the densities that is just like the equation for
the XAFS, but valid for each angular momentum state.
Just as
mu(E) = mu_0(E) * ( 1 + chi(E) )
with the implicit assumption that mu, mu_0, and chi are all evaluated
for the final state angular momentum, you can write this equation:
rho_l(E) = rho_{l,0}(E) * ( 1 + chi_l(E) )
for each angular momentum state. The rhol files contain rho_l(E).
The rhoc files contain rho_{l,0}(E).
HTH,
B
--
Bruce Ravel ----------------------------------- ravel@phys.washington.edu
Code 6134, Building 3, Room 405
Naval Research Laboratory phone: (1) 202 767 2268
Washington DC 20375, USA fax: (1) 202 767 4642
NRL Synchrotron Radiation Consortium (NRL-SRC)
Beamlines X11a, X11b, X23b
National Synchrotron Light Source
Brookhaven National Laboratory, Upton, NY 11973
My homepage: http://feff.phys.washington.edu/~ravel
EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/