[Wien] (no subject)

[Peter Blaha]

> intensity], I want to compare my reslut by LSDA+SO+SIC method with this
> XPS, the questions are the followings:
>
>     1.Can we directly compare the total density of states of the unit cell
> with the XPS? Someone has commented that the relative  strength of XPS
> features should in general be different   from those of  the density of
> states, as the latter does not include the  shell-dependent  cross
> sections.
>  This may in agreement with the userguide about  the XSPEC, which tell us
> that theoretical X-ray spectra are generated using the partial densities of
> states (in case.dos1ev)and multiplying them with the corresponding dipole
> matrix elements. Can we relate the dipole matrix elements with the
> shell-dependent cross section?

You are mixing up something:
Please note: XSPEC is for X-ray absorption or emission spectroscopy. These
spectroscopies involve a core-level + valence/conduction level and are
thus site (=atom) and "dipole" sensitive. You measure photons!!!

XPS/UPS on the other hand involves only one (bound) state!! and you measure
the outcomming electron. This electron is excited by some "X-rays/UV", but
usually you take a radiation of a certain wavelenght and the crosssection
is now dependend on this radiation.

For UPS you can (to some extend) take to DOS, and if you know the
crosssections for the different atoms you can add up all partial DOS times
corresponding crosssections.
Unfortunately, to my knowledge XPS agrees at best qualitatively, while XES/XAS
agrees much more quantitatively.



                                      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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