[Wien] How close one can get to experimental XPS line of C1s in graphene by WIEN2K

[Peter Blaha]

I don't think there is any guidance for XPS in the UG. There should be
some hints in the transparencies of our WIEN2k-workshops.

XPS (measures the ionization energy of a C 1s electron) is different from
XAS.

The eigenvalues are NOT a good approximation for ionization energies,
but according to Slater's transition state theory, eigenvalues at
half occupancy are a reasonable approximation.

So you should set the 1s occupation to 1.5 in case.inc (and add half an electron
as background charge in case.inm). After scf, the 1s energy of this C 1s
orbital is a fairly good approximation (don't expect too much !, such
calculations are more usefull to compare relative shifts between
2 compounds than absolute numbers)


Am 21.09.2010 13:33, schrieb Markus Kaukonen:
> Dear WIEN2k,
>
> I calculated the value for XPS line of C1s in graphene using WIEN2k.
>
> My settings:
> 6x6 graphene lattice with un-optimised lattice constant (2.45 Å)
> at gamma point using  R-MT*K-MAX=5.0, XC=PBE-GGA.
> With the same geometry I set 1S electron of a carbon atom to valence
> (as in the wien2k manual sec 10.4).
>
> My result:
> 292.2 eV, experimental value 284.6 eV (did not get proper reference,
> now using Kim et al., Electrochemistry Communications, v.3, pp
> 608--612 (2001)).
>
> Question:
> Should I be happy with this value or does one get much closer by
> converging all the parameters properly?
>
> Terveisin, Markus
>

-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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