Diego, Your question is not completely clear to me, but here's my stab. Starting from the nominal (i.e. without interstitials) crystal structure, have Atoms export a P1 file, which is the same crystal structure but with the fully populated unit cell and the space group set to "p1". Insert whatever atoms you think need to be there. Run Atoms again on the new input structure. ??? Profit! B On Wednesday, June 27, 2012 10:41:31 AM Diego Fernando wrote:

For some time I'm using FEFF8.4 for calculations of absorption-XANES and DOS in some superconducting materials for which it has been successful, now I have the need to include in the'' input "of some impurity atoms in interstitial positions by Example:

*A* *1.16* *B* where *A* and *B* are two different species of atoms, I made ​​several attempts in trying to implement this using ATOMS3.0 on the web:

http://millenia.cars.aps.anl.gov/cgi-bin/atoms/atoms.cgi

but I have not had consistent results, in ATOMS3.0 manual explains that the program has been designed for this, but suggests that it may be possible. I appeal to you to see if I can help solve this problem. Thanks for your attention.

Diego Fernando Mulato Gómez. Estudiante de doctorado en Física Teórica, CINVESTAV, Unidad Mérida, México.

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