[Ifeffit] Too Many Atoms

The problem that I have is that with 141 crystallographic sites for a DNA molecule and a space group p 4 2 2, I end up with 611 atoms after running ATOMS. This gives me the error: Feff 6L.02 Fatal Error: Too many atoms in ATOMS list. Maximum is 500. I tries decreasing the number of crystalographic sites by removing hydrogen atoms, but then I got another error: Feff 6L.02 No atoms or overlap cards for unique pot 1 Cannot calculate potentials, etc. Fatal Error: at RDINP. I tried increasing the Rmax as indicated, but this only served to increase the number of atomes, leading me to the error given above. I was hoping that someone could help me with this problem. Remko van den Hurk