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