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#1 | XPS spectra calculated by FLEUR datum

Sun Apr 25, 2021 3:48 pm

Dear all users of FLEUR,

I would like to use the FLEUR-code to calculate the energy levels of the inner-shell electrons in the case of elemental substitution. In other words, I would like to know the energy atomic energy levels of the inner-shell electrons of the surrounding atoms when some of the atoms in the supercell are changed to various atoms. Of course, it is difficult to calculate the absolute value of the energy levels, but we hope to know the relative energy change (chemical shift).

I know that part of the JL-VMD project is creating a database of XPS spectra of various alloys. FLEUR-code is used for the calculation of this database, but I could not understand how to calculate XPS spectra although I read the manual.

The method for calculating XPS spectra is patented, but is it not available to the public at this time? I would appreciate it if someone could tell me how to do it.

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#2 | RE: XPS spectra calculated by FLEUR datum

Thu May 06, 2021 7:36 pm

FLEUR actually calculates the core electron levels in each standard self-consistency cycle. Hence, it is relatively straight forward to obtain the core levels for a supercell with e.g. a defect for all core levels of the unit cells. As you said, the absolute values usually are of little use, but by comparison with a suitable reference system one can easily calculate shift which tend to be rather reliable. Please note in addition: Core levels are somewhat sensitive to the radial grid as given by the MT radius, the grid-points and the log. Increment. Hence, keep these values consistent when comparing energies!

FLEUR can also calculate partially occupied core configurations that can be used in a Slater transition state manner to obtain more realistic shifts by also including static screening effects.

Hope this helps,

Daniel

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#3 | RE: XPS spectra calculated by FLEUR datum

Tue May 18, 2021 9:39 am

Hi Hidemaru,

Thanks for you interested in this. To add to Daniels answer:
The theoretical spectra are formed by placing peakfuntions at the calculated shifted core-level positions.
The type of the peakfunction (voigts or some asymmetric profiles) depends on the element and core-level. The peakfunction parameters are fitted within the evaluation, since besides the influence from the experimental apparatus we cannot calculate the lifetime broadenings, screening and other things accurately within simple DFT.

What is currently a patent application is the 'data-driven chemical evaluation procedure' of XPS spectra.
We have a small program to do such evaluations. It is not public (at this time), but you can request it here (remove space in link):
www. inventionstore.de/angebot/5654/

which is probably free if you are working in academia.

For further references how it is done and what is currently possible I refer you to my PhD thesis (remove space in link):
https:// juser.fz-juelich.de/record/891865/
(Papers on this are not out yet)

If you have further questions feel free to ask.
Best regards and sorry for the late reply,
Jens

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� Convergence of XPS core levels