[Ifeffit] Artemis fitting using FEFF paths plus experimental references

[Matthew]

I have a system in which Fe:C alloy nanoparticles are being oxidized.  I have the EXAFS of the unoxidized nanoparticles, and I'd 
like to use that as a reference
for fitting as in:

Fe_EXAFS(oxidation_stage) = x*(unox_particles)+(1-x)*(Fe->O paths + Fe->Fe paths +...)

where the Fe->O and Fe->Fe are based on magnetite and maghemite, which seem to be products of the oxidation.  It's not just a linear 
fit to
unoxidized+magnetite+maghemite because the oxide is somewhat disordered. If I do Artemis fits to the shells from the two oxides 
alone, I find I lose
some Fe atoms (sum of fractions < 1), a result which is echoed in linear-combo fits to the oxides alone.  Thus, I really want to do 
a hybrid fit.  The unoxidized
particles are highly disordered to the point where they don't fit well with reasonable shells, so I'd rather not have to represent 
them as FEFF shells.

How can I do this hybrid fit?
    mam