[Wien] Wrong result of XSPEC with high grid resolution

[backes at th.physik.uni-frankfurt.de]

Dear Wien2k users,

I want to reproduce the Mg K-edge X-ray absorption spectra shown in Prof.
Blaha's slides as found here:

http://www.wien2k.at/reg_user/textbooks/WIEN2k_lecture-notes_2011/Blaha_xas_eels.pdf

I followed the userguide and the instructions from the slides:

Set up a 2x2x2 supercell of MgO (make one Mg inequivalent)
Remove one core electron in MgO.inc
Add one valence electron in MgO.in2c
Run the selfconsistency cycle
Remove valence electron from MgO.in2c
Calculate spectra with "x xspec".

With this I can almost exactly reproduce the result.
But I noticed a problem when using higher resolution of the spectrum.
Going down to DE=0.004eV everything looks nice and nothing changes except
for more data points.
But when going lower, e.g. DE=0.0035eV I suddenly get wrong results. Huge
peaks are popping up in the spectrum that haven't been there before.
Is there a problem with the code for high resolution?

I'm using Wien2k v13 with the Intel 13.1.1.163 Compiler.
My MgO.inxs file looks like this:

----Start of MgO.inxs -----------------
MgO Mg-hole absorbtion
4              (atom)
1               (n core)
0               (l core)
0,0.5,0.5       (split, Int1, Int2)
-1,0.004,20      (EMIN,DE,EMAX in eV)
ABS             (type of spectrum)
1.6            (S)
0.3            (gamma0)
----End of MgO.inxs -----------------

best regards,
Steffen Backes