[Wien] N1s binding energy in TiN

[Peter Blaha]

Sorry for the confusion. The quoted values in the pdf are probably from 
a lousy calculation and are ment only to demonstrate the effect (if I 
remember correctly, only a 4x bigger P supercell, but for sure not 
converged, I also don't remember which functional, ....) and only 
accidentally match experiment.

My general experience is that core-eigenvalues (taken with respect to EF 
!!) are 10-15% off, while slater TS gives 1-2 %, i.e. an order of 
magnitude better.


On 1/17/19 9:15 AM, Pavel Ondračka wrote:
> Dear Wien2k mailing list,
> 
> I'm looking for some advice regarding the calculation of core level
> binding energies (to compare with XPS experiments). First of all there
> is this nice lecture where prof. Blaha actually shows some calculations
> http://susi.theochem.tuwien.ac.at/reg_user/textbooks/WIEN2k_lecture-
> notes_2011/Blaha_xas_eels.pdf of core levels with perfect results. For
> example with TiN the deltaSCF method gets 397.1eV for the N1s level as
> compared to 397.0eV experiment. The trouble is that I'm not able to
> reproduce this.
> 
> I've done some calculations before and I was never really happy with
> the absolute values which were always few eV off but I've always
> thought this is just the limitation of xc functional or methodology.
> Hence seeing the nice results in the lecture surprised me. However, I'm
> not able to reproduce the values even for metals from the example. For
> the TiN I'm getting values of 404.8eV with the slaters transition state
> approach and 404.6eV with delta-scf (here I'm using the formula for
> metals E_b = E^tot_initialstate(N) - E^tot_finalstate(N), i.e. placing
> the core-electron in the valence band and with PBE). I have thought
> that this is maybe functional difference, since while taking LDA
> instead of PBE shifts the results differ almost by 4eV (to 400.9eV).
> However with the PBE I get the core energy ε_i as 377.4eV (consistent
> with the mentioned pdf where it is 377.5eV) so maybe this is not just
> about functional?. I've already checked convergence with supercell size
> as well as numerical parameters and I'm actually out of ideas.
> 
> To be honest, I'm not much concerned personally about the discrepancy
> since the chemical shifts seem to be reasonable even if the absolute
> values are not. I just think that if it is possible to get the absolute
> values right (or at least closer to experiment) as in the lecture pdf,
> the results would of course look way better, therefore I'll be grateful
> for any comments and help.
> 
> Best regards
> Pavel
> 
> 
> 
> 
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
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