Hi Kristine,
This is actually a feff.inp question.... but I'm hoping someone might be able to clarify this for me...
I hope someone can provide better insight for Feff8, but here's what I'd say:
I was wondering what appropriate values are for l_scmt, l_fms, and stoichiometry for the feff.inp I'm working with regarding Au on a Ni surface (I'm fitting with feff calculations with either a single Au atom in the first Ni layer or two Au atoms in the first Ni layer)?
Should they all be the same for each potential?
For EXAFS and EXAFS fitting, the FMS and XANES calculations should not be done. For EXAFS, these values don't matter (I think!). For what it's worth, L_fms basically sets how high in k the FMS approach works well enough to use. It's typically a number <~ 5. I'm not sure what l_scmt is...
(i.e. in the past I have used the following for 2 Au's in the surface) POTENTIALS * ipot z element l_scmt l_fms stoichiometry 0 79 Au 3 3 0.001 1 28 Ni 2 2 4 2 79 Au2 3 3 4
Oh, I think those might be ipot z element lmin lmax and that lmin=-1, lmax=3 are reasonable default values. Hopefully someone can clarify this....
Oh... one more question... I haven't been using the ellipticity card in the feff.inp file, even though I've been using "POLARIZATION 1 0 0"... is this OK?
Yes, the ellipticity card is for describing polarizations that are not linear, such as for magnetic circular dichroism. For your surface EXAFS experiments at APS 5-ID, the x-rays were highly linearly polarized. Hope that helps, --Matt