[Wien] Odd result (that may be correct)

[Laurence Marks]

I have an odd result that is probably correct; hopefully someone has come
across the relevant physics before and can give me a clue.

The case is complicated. I have a rocksalt structure (389 atom supercell)
based upon NiO with 2Cr3+ substituted for 3Ni2+ semirandomly, calculated
with -eece 0.25 for Ni & Cr, and closely following antiferromagnetic
ordering. As it was semirandomly generated, it is not exactly
antiferromagnetic, and the unit has a nett moment of -2. It is a decent
insulator.

When analyzing the EELS spectra of the Ni L (no core hole), there is a
~0.8eV shift to higher energy in the first peak for the Ni atoms with +2
spin (~1.72 inside the RMT) relative to those with -2 spin. This seems to
"make sense" as an exchange energy of the unoccupied states with the mean
spin of the unit cell. (It is not related to the core states, so can only
be the unoccupied states.) Does this ring a bell with anyone?

-- 
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu
Corrosion in 4D: www.numis.northwestern.edu/MURI
Co-Editor, Acta Cryst A
"Research is to see what everybody else has seen, and to think what nobody
else has thought"
Albert Szent-Gyorgi
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