[Wien] Ambiguity in instructions for XPS/XAS/TELNES

[Laurence Marks]

We are focusing on the Ni edges, and want to compare several different
compounds so relative positions etc matter. From reading txspec.f it looks
as if for O the effect should be small, but I don't see justification for
the Ni valence states being used.

Maybe someone has tested this previously in detail and can respond.

On Thu, Feb 16, 2017 at 7:40 AM, Peter Blaha <pblaha at theochem.tuwien.ac.at>
wrote:

> If this is O-K edge, then one can keep NE in in2 file constant and
> neutralize in mixer (inm).
> I think this option is mentioned somewhere for cases when the first
> unoccupied states have a very wrong character as supposed from the
> dipole selection rule.
>
> Am 16.02.2017 um 00:38 schrieb Laurence Marks:
> > Thanks. The postdoc is running cases (NiO supercell) which are not
> > completed yet; there are differences but I will wait.What concerns me a
> > little is that no matter what type of core hole one uses, the extra
> > electron added in case.in2 will go into the minority d unless fsm is
> used.
> >
> > On Wed, Feb 15, 2017 at 3:56 PM, Peter Blaha
> > <pblaha at theochem.tuwien.ac.at <mailto:pblaha at theochem.tuwien.ac.at>>
> wrote:
> >
> >     I do not have real experience with this and I don't think there are
> >     "global" rules, but one has to consider the specific case.
> >
> >     I guess in most cases it does not matter which spin you select for
> the
> >     core hole. The important thing is the coulomb potential, which is
> >     modified due to a missing electron. The exchange effect should be
> small.
> >
> >     I could imagine (without real experience) that this could be
> important
> >     for more localized cases like in 3d or in particular 4f elements,
> >     because the 4f valence electrons are spatially in a similar region
> as a
> >     higher core electron and thus direct exchange effects can happen.
> >
> >     In any case, typically XAS of localized 3d or 4f electron systems is
> not
> >     well described by the simple core-hole approach, since multiplet
> effects
> >     dominate the L2,3 or M4,5 spectra.
> >
> >     PS: Did you really see a spin change depending on a up/dn or
> >     "non-magnetic" hole ?
> >
> >     Am 15.02.2017 um 17:41 schrieb Laurence Marks:
> >     > Also...there might be a deeper problem since if one uses an "up"
> core
> >     > hole, unless FSM is used the final state can have a spin change.
> >     >
> >     > On Tue, Feb 14, 2017 at 4:24 PM, Laurence Marks
> >     > <L-marks at northwestern.edu <mailto:L-marks at northwestern.edu>
> >     <mailto:L-marks at northwestern.edu <mailto:L-marks at northwestern.edu>>>
> >     wrote:
> >     >
> >     >     I think there is a slightly ambiguity for spin-polarized cases
> in
> >     >     the UG. I don't see mention that one has to carefully setup
> >     >     case.incup/case.incdn for the core hole (or fractional hole).
> From
> >     >     what I can see it does not seem like this is an issue in the
> later
> >     >     calculations, but I think it is easy for someone to
> inadvertantly
> >     >     calculate a spin-unresolved for for a spin case.
> >     >
> >     >     N.B., for my own sanity, it would be nice if someone could
> confirm
> >     >     that xtelnes/xspec don't really care about the occupancies in
> >     >     case.inc, just an adequate list of states.
> >     >
> >     >     --
> >     >     Professor Laurence Marks


-- 
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu ; Corrosion in 4D: MURI4D.numis.northwestern.edu
Partner of the CFW 100% program for gender equity, www.cfw.org/100-percent
Co-Editor, Acta Cryst A
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