[gpaw-users] Calculating core-level shifts between different systems

[Eric Hermes]

Hello,

I wish to calculate the core-level shift of the Pd 3d 5/2 state in PdO, 
PdO2, and Pd-Te intermetallics with respect to metallic Pd in order to 
compare against experimental XPS spectra. The experimentalists indicate 
that the presence of Te in the intermetallic shifts the Pd 3d 5/2 state 
to higher binding energy, but my chemical intuition coupled with Bader 
analysis indicates the opposite. I have attempted to calculate these 
properties in VASP (using the ICORELEVEL tag), but the oxide shifts do 
not even semi-quantitatively agree with experiment (although they do 
agree qualitatively, as the shifts are ordered correctly). Part of the 
ambiguity here is that I am unsure what to take as the zero of energy in 
fully 3D periodic systems to properly compare binding energies.

I believe that GPAW might be better able to calculate these values, as I 
can do 2D-periodic slab calculations which have a true zero reference 
energy. However, I am slightly confused by the information on this page:
https://wiki.fysik.dtu.dk/gpaw/tutorials/xas/xas.html
The citation Leetmaa2006 seems to be missing, and I cannot find what 
paper this refers to. I am unsure of what exactly is being calculated in 
the "Further considerations" section; is this how one compares to 
experimental XPS spectra? Can someone help guide me in doing these 
calculations within GPAW?

Thank you,
Eric Hermes

-- 
Eric Hermes
J.R. Schmidt Group
Chemistry Department
University of Wisconsin - Madison