EXAFSPAK is a suite of XAS data analysis programs developed by Dr. G.N.
George of SSRL.
Features include a degree of automation, an efficient curve-fitting
algorithm using analytically
calculated derivatives (allowing more rapid convergence to the best-fit
than with numerically
calculated ones). Other features include the ability to link different
variables together in the
curve-fitting process, and the availability of search routines and
best-integer fitting functionality.
The curve-fitter can utilize the ab initio multiple scattering code FEFF
More information is available from here