What kind of particular expertise can we offer to the mankind?

Well - we assume that you are an expert in x-ray spectroscopy, so we are not going to pretend that the Earth would stop its rotation if our group stopped doing physics. If you are interested in truly classy researchers, you've got to look around somewhere else. Nevertheless, we believe that we are still able to offer some prospectively useful and valuable "hands-on" experience, mainly in the following areas:

Polarized spectra:

We have quite a bit of experience with analyzing polarized (i.e., angularly dependent) x-ray absorption and x-ray emission spectra (check our publications dealing with polarized XANES of various materials). We realized gradually that polarized spectra pose actually a much more stringent test of the theory than unpolarized spectra do: It may happen that while, say, a one-electron RS-MS approach sufficiently reproduces polarizationally averaged (polycrystal) spectra, it fails at the same time to reproduce significant features in polarizationally resolved curves.

Quadrupole transitions:

Quadrupole transitions were incorporated into our RSMS code, so we can account for them in our XANES calculations "routinely". We have fussed a bit with them while analyzing spectra of V₂O₅and CuO. However, it in many cases the photoelectron energy region where quadrupole contributions are significant coicides with region where effective one-electron approach is no longer valid (those bloody oxides...). So one should pay extra care in these situations: The nature would not probably approve all the quadrupole peaks we calculate.

Self-consistent muffin-tin potentials:

For quite a long time, real-space calculations of XANES routinely relied on non self-consistent potentials constructed according to the so-called "Mattheiss prescription" (superposition of potentials and electron densities of isolated atoms). Potentials generated in this simple way proved to be quite suitable for many materials and/or edges, making it thus possible to exploit XANES analyses even for complicated systems for which obtaining self-consistent potentials through band-structure calculation would be impractical (not mentioning the core hole...). However, you cannot live without self-consistent potentials for ever and so we started to use self-consistent potentials as well - at least from time to time.
We obtain self-consistent muffin-tin potentials in a two-fold way: (i) For complex materials, it seems to be quite practical to get self-consistent potentials from cluster rather than from band-structure calculations. Thus we perform a MS X-alpha calculation for a molecular cluster of 10-20 atoms, obtaining thereby self-consistent potentials for later use. We employing an amended version of the XASCF code of Case and Cook for the X-alpha molecular calculation. (ii) We also developped a method for constructing effective one-electron potentials from full-electron charge densities which we obtain from all-electron pseudopotential calculations. Doing all-electron pseudopotential calculations is not a trivial business and obtaining "normal" potential from a pseudopotential is not that simple either. Nevertheless, it can be done and we encourage you to learn more about it.

Non-muffin tin effects:

We bet that the bulk of all calculatons of XANES spectra the mankind does is performed within the so-called "muffin-tin approximation". Within that approximation, the efective one-electron potential is assumed to be spherically symmetric inside spheres ascribed around each of the nuclei and is set to a constant in the interstitial region, i.e., between the spheres. This approximation works quite well in typical situations. The trouble is, sooner or later you run into a non-typical situation and then you've got problems. Few approaches overcoming this problem in that or other way were elaborated. Our way of dealing with the issue relies on a consistent use of the pseudopotential technique of electronic structure calculations. This technique does not introduce any assumptions about the shape of the electron potential and, contrary to some other approaches, is able to provide self-consistent non-muffin-tin potentials as well. There is just a "minor" hurdle to overcome, namely, that the pseudopotential method does not provide true wave functions if applied in a standart way. So one has to employ a special method of reconstructing true electron wave functions by solving Schrodinger equation in the neighborhood of isolated atoms while satisfying certain matching conditions. Some applications of this novel approach for XANES calculation yielded interesting results, however, we haven't gone the full way yet.

Connection between XANES spectral features and real structure:

To find some sort of fingerprints of real structure units in XANES spectra seems to be a very complicated task, possibly with no unique solution. We got involved in few analyses of the influence of changes of real structure on the shape of XANES spectra for specific systems and we gathered some hand-on experience with this kind of stuff. We don't think the mankind has said its last word on employing XANES for structural studiest so far. Only one thing seems to be sure already: It is a complicated business.

Photoelectron wave function probability densities:

It's a quite a common situation: You calculate something, you even trust your results (quite a rare occasion, we know ...) but you lack an intuitive understanding our your data. Sometimes you don't just want to calculate something but you want to know what on earth have you calculated. In fact, when analyzing x-ray spectra, this is quite a common urge. In the RS-MS framework, everyone talks about scattering events and electron paths and so on - but what is there really going on, where the excited photoelectron really is? We believe the wave function probability density concept pursued by our group provides the most sensible answer to this naively-sounding question. This kind of analysis certainly does not solve all the problems connected with applications of XANES analysis for structural studies, neverthless, by providing an answer to a well-defined question it may facilitate intuitive understanding of the origin of particular spectral peaks.

X-ray emission spectroscopy:

"Ordinary" non-resonant x-ray emission may not be among the most sexy spectroscopic methods at the moment. Photoelectron emission spectrocopy is more often the method of choice if you are interested in investigating electronic structure of solids. Nevertheless, the chemical selectivity of XES may still be a big assett when it comes to impurities, overlayers etc. Our group has a long and established tradition in theoretical modelling and interpreting of x-ray emission spectra.