Bruce,

thanks for your answer, it is a great problem to increase the number of atoms, huge CPU time is needed to finish a calculation.

Here I pasted the header and the first lines of the atom list and attached the whole file, if somebody could help me to reduce the calculation time I will be grateful.

Thanks in advance, euG

 * This feff8 input file was generated by Artemis 0.8.011

 * Atoms written by and copyright (c) Bruce Ravel, 1998-2001

 TITLE name: ZnO:Er 1 at no distortion d= 4.136
 TITLE formula: ZnO
 TITLE sites: Zn1,O1
 TITLE refer1: wyckoff, vol 1, ch III, p 111
 TITLE refer2:
 TITLE schoen:
 TITLE notes1:

 * Er L3 edge energy = 8358.0 eV
 EDGE L3
 S02 1.0

 * pot xsph fms paths genfmt ff2chi
 CONTROL 1 1 1 1 1 1
 PRINT 3 0 0 0 0 0

  *** ixc=0 means to use Hedin-Lundqvist
 * ixc [ Vr Vi ]
 EXCHANGE 0

  *** Radius of small cluster for
  *** self-consistency calculation
  *** A sphere including 2 shells is
  *** a good choice
  *** l_scf = 0 for a solid, 1 for a molecule
 * r_scf [ l_scf n_scf ca ]
 SCF 4.0

  *** Upper limit of XANES calculation.
  *** This *must* be uncommented to
  *** make Feff calculate full multiple
  *** scattering rather than a path expansion
 * kmax [ delta_k delta_e ]
 XANES 4.0

  *** Radius of cluster for Full Multiple
  *** Scattering calculation
  *** l_fms = 0 for a solid, 1 for a molecule
 * r_fms l_fms
 FMS 5.00 0

  *** Energy grid over which to calculate
  *** DOS functions
 * emin emax eimag
 LDOS -30 20 0.1

  *** for EXAFS: RMAX 12.0 and uncomment
  *** the EXAFS card
 RPATH 0.1
 *EXAFS 20

 POTENTIALS
 * ipot Z element l_scmt l_fms stoichiometry
  0 68 Er 3 3 0.001
  1 30 Zn 2 2 2
  2 8 O 1 1 2
  3 68 Er 3 3 2

 ATOMS * this list contains 902 atoms
 * x y z ipot tag distance
  0.00000 0.00000 0.00000 0 Er 0.00000 0
  -0.93804 -1.62473 -0.49466 1 Zn1 1.94019 1
  1.87611 0.00002 -0.49466 1 Zn1 1.94023 2
  -0.93804 1.62477 -0.49466 1 Zn1 1.94023 3
  -0.93804 -1.62473 1.30173 2 O1 2.28346 4
  0.93804 1.62473 -1.30173 2 O1 2.28346 5
  1.87611 0.00002 1.30173 2 O1 2.28348 6
  -0.93804 1.62477 1.30173 2 O1 2.28348 7
  -1.87611 -0.00002 -1.30173 2 O1 2.28348 8
  0.93804 -1.62477 -1.30173 2 O1 2.28348 9
  0.93804 1.62473 2.10879 1 Zn1 2.82253 12
  -1.87611 -0.00002 2.10879 1 Zn1 2.82255 13
  0.93804 -1.62477 2.10879 1 Zn1 2.82255 14
  0.93804 1.62473 -3.09811 1 Zn1 3.62187 21
  -1.87611 -0.00002 -3.09811 1 Zn1 3.62189 22
  0.93804 -1.62477 -3.09811 1 Zn1 3.62189 23
  -3.75219 0.00002 -0.49466 1 Zn1 3.78466 24
  1.87611 -3.24948 -0.49466 1 Zn1 3.78465 25
  1.87611 3.24952 -0.49466 1 Zn1 3.78469 26
  -3.75219 0.00002 1.30173 2 O1 3.97158 27
  1.87611 -3.24948 1.30173 2 O1 3.97158 28
  -1.87611 3.24948 -1.30173 2 O1 3.97158 29
  3.75219 -0.00002 -1.30173 2 O1 3.97158 30
  1.87611 3.24952 1.30173 2 O1 3.97161 31
  -1.87611 -3.24952 -1.30173 2 O1 3.97161 32
  2.81415 1.62475 2.60345 3 Er 4.16380 33
  -1.87611 3.24948 2.10879 1 Zn1 4.30417 45
  3.75219 -0.00002 2.10879 1 Zn1 4.30418 46