[Ifeffit] Fitting EXAFS with out any atomic coordinates?

Hi Bruce my name is Mario and I was just wondering if your program can fir the EXAFS spectra without any atomic positions. Obviously the answer is no if you use atoms to create the FEFF file but what does one do when we have a semi-crystalline material for which no one has attempted the fractional coordinates. I mean the XRD pattern shows some crystalline but due to the high background I would think it would be very hard to do the Rietveld analysis. So what can one do, can we fit the EXAFS spectra knowing only the chemical composition and perhaps the lattice geometry(orthorhombic or hexagonal)? thanks