Dear I have some problem with some very easy simulations with FEFF. Everytime I introduce a second element in the matrix in this way POTENTIALS 0 26 Fe 1 26 Fe 2 29 Cu the simulation does not work and it stops with a message that you can read in the attached document. But the program works perfectly with the monoatomic potential POTENTIALS 0 26 Fe 1 26 Fe I do not understand what there is written in the feff-message, so I will appreciate any suggestion. Thank you in advance for your precious help. Sebastiano Cammelli