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