Hi, I want to remind everyone that it is important to use the mailing list. I do not feel that I am obligated to answer questions about the software that come to me by any other channel, particularly when I do not have a personal relationship with the person asking the question. That said, I am forwarding this fellow's question to the mailing list and providing an answer. Thitipong, this is a case of GIGO. According to Acta Cryst. (1972). B28, 3102-3103 (the reference I found for Cr23C6): The crystal structure of chromium carbide, C r 2 3 C 6 , has been described as cubic, space group Fm3m, 4Cr (I) in (a) (000), 8Cr (II) in (c) (l-lq:), 48Cr (III) in (h) (Oxx), x= 0.165, 32Cr (IV) in (f) (xxx), x=0.385, 24C in (e) (x00), x=0-275 (Westgren, 1933) on the basis of X-ray single crystal and powder diffraction data. We have confirmed this structure and determined the atom positions more precisely by a neutron diffraction study of a powder sample. Using those coordinates, I have no problem running atoms and feff. The structure is a bit strange -- I guess this is more like a metal than a carbide -- but it seems consistent with the paper after a cursory inspection. According to http://www.crystallography.net/cod/1009019.html, the space group for Cr7C3 is P M C N. Atoms and feff run fine with this input data. Some hints on asking questions that so you'll get the answers you are looking for: http://bruceravel.github.com/demeter/pods/bugs.pod.html http://bruceravel.github.com/demeter/pods/help.pod.html B -------- Forwarded Message -------- Subject: FEFF trouble help me please !!!! Resent-Date: Fri, 3 Jul 2015 04:25:57 +0000 Resent-From: bruce.ravel@nist.gov Date: Fri, 3 Jul 2015 11:33:12 +0700 From: Thitipong Po-Kloy To: bruce.ravel@nist.gov Hi Bruce , My name is Thitipong . I have trouble about FEFF program and believes you can help me. Now I am doing "XANES simulation" Cr23C6 and Cr7C3 . So , when I run FEFF program - it report TWO ATOMS VERY CLOSE TOGETHER . How can I fix it ? This it Data of atom Cr23C6 title name : Cr23C6 title formula : Cr23C6 space F M 3 M a=10.6599 b=10.6599 c=10.6599 rmax = 10 core=Cr1 atom Cr 0 0 0 Cr1 Cr 0.25 0.25 0.25 Cr2 Cr 0.385 0.385 0.385 Cr3 Cr 0 0 0.340 Cr4 C 0.276 0.276 0.276 C1 and Cr7C3 title name : Cr7C3 title formula : Cr7C3 space P M C M a=7.0149 b=12.1530 c=4.5320 rmax = 10 rpath=6 core=Cr1 atom Cr 0.064 0.811 0.056 Cr1 Cr 0.250 0.626 0.057 Cr2 Cr 0.250 0.206 0.250 Cr3 Cr 0.250 0.416 0.261 Cr4 Cr 0.065 0.021 0.250 Cr5 C 0.250 0.562 0.459 C1 C 0.029 0.342 0.028 C2 If there is any other way please let me know. Thank You , Thitipong -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Science Group at NSLS-II Building 535A Upton NY, 11973 Homepage: http://bruceravel.github.io/home/ Software: https://github.com/bruceravel Demeter: http://bruceravel.github.io/demeter/