[Wien] calculation of binding energy

[Michael Gurnett]

The "delta-SCF" calculations that you mention, is this the same as the Z+1 
technique. I've been using the Slater transition state technique which I 
find works well with the exception that on slabs it shifts the core levels 
of the surface atoms "to far" to lower binding energies in comparison to 
bulk like atoms. Would it be possible that techniques like these are put on 
the faq page.

regards
Michael
----- Original Message ----- 
From: "Peter Blaha" <pblaha at zeus.theochem.tuwien.ac.at>
To: <wien at zeus.theochem.tuwien.ac.at>
Sent: Wednesday, December 15, 2004 8:15 AM
Subject: Re: [Wien] calculation of binding energy


> Of course one MUST NOT simply look at the core eigenvalues and compare 
> them
> with experiment. There are two reasons behind,
> i) The energy zero, which will be different for different calculations.
> You can try to get the "trends" right, when comparing the E-differences
> between the core state and EF (and consider the experimental workfunction,
> which might also contribute when different for different compounds).
>
> ii) DFT eigenvalues are in principle NOT the ionisation energies which you
> measure in experiment. Errors of more than 10% are typical.
>
> To overcome this, you have to do either "Slater's transition state" or
> "delta-SCF" calculations. For both methods you have to create a core hole
> (half a core hole for Slaters t.st.) and do a calculation with this
> core hole (change inc manually, add this electron in the valence (in2);
> eventually break symmetry or generate a small supercell so that the core
> hole is just on one of the atoms). Then you look at the eigenvalue 
> (Slater)
> or at the total energy differences.
>
> I guess there are several papers on core-level shifts with WIEN in 
> literature.
> Relative shifts should be quite precise, absolute binding energies have 
> errors
> of 1% (if I remember correctly).
>
>> I am trying to compare experimental (XPS) binding energies to 
>> calculations for
>> S atoms in different Ni sulfides with different structures and 
>> co-ordination.
>>
>> The core state energies calculated by Wien are quite different from 
>> experiment
>> and FEFF8 calculations. I assume this is because the zero in the Wien
>> calculations is the average Coulomb potential not the the vacuum level. 
>> We are
>> also seeing that the trends in the core level energies are different for 
>> Wien
>> than experiment and FEFF.
>>
>> Does anyone have any advice on how to go about comparing calculated and
>> experimental binding energies and also on how reliable we might expect 
>> them to
>> be?
>>
>> Thanks and best wishes to you all,
>>
>> Regards
>> Vicki
>>
>> -- 
>> --------------------------------------------------------------------------------
>> ---
>> Dr. Vicki J. Keast
>> Australian Key Centre for Microscopy and Microanalysis
>> Madsen Building F09
>> University of Sydney
>> Sydney NSW 2006
>> Ph: + 61 2 9351 4523
>> Fax: + 61 2 9351 7682
>> email: v.keast at emu.usyd.edu.au
>>
>> For correspondence regarding the Australian Microscopy and
>> Microanalysis Society, please reply to amms.secretary at emu.usyd.edu.au
>> --------------------------------------------------------------------------------
>> --
>>
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>
>
>                                      P.Blaha
> --------------------------------------------------------------------------
> 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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