Hi, I was trying to simulate Cu2O...cubic...O tetrahedrally coordinated by Cu...Cu linearly coordinated by O. There are two origin choices for space group 224 (Pn-3m). If using origin choice 1, then atom positions would be O    0,0,0 Cu  0.25,0.25,0.25 If using origin choice 2, translate by -0.25,-0.25,-0.25 to get O  0.75,0.75,0.75 Cu  0,0,0 (or use the shift vector in Atoms...) My understanding is that Demeter defaults to the 2nd origin choice. Problem I am having is that neither gives me linearly coordinated copper using current Atoms. If I read in the attached atoms.inp (choice 2) and Run Atoms, the ATOMS list in the Feff output begins with:  ATOMS                  * this list contains 87 atoms  *   x          y          z     ipot tag           distance     0.00000    0.00000    0.00000  0  cu1           0.00000    -1.06675    1.06675    1.06675  2  o1.1          1.84767    -1.06675   -1.06675    1.06675  2  o1.1          1.84767     1.06675    1.06675   -1.06675  2  o1.1          1.84767    -1.06675   -1.06675   -1.06675  2  o1.1          1.84767      2.13350    2.13350    0.00000  1  cu1.1         3.01722 I get 4-coordinate instead of 2-coordinate. If I try origin choice 1, almost the same result....  ATOMS                  * this list contains 83 atoms  *   x          y          z     ipot tag           distance     0.00000    0.00000    0.00000  0  cu1           0.00000    -1.06675    1.06675    1.06675  2  o1.1          1.84767     1.06675   -1.06675    1.06675  2  o1.1          1.84767     1.06675    1.06675   -1.06675  2  o1.1          1.84767    -1.06675   -1.06675   -1.06675  2  o1.1          1.84767     2.13350    2.13350    0.00000  1  cu1.1         3.01722 If I run choice 1 with the shift vector, I do reproduce the choice 2 result.  If I use the old dos version of Atoms with origin choice 2, I do get linearly coordinated copper:  ATOMS     .00000      .00000      .00000    0   cu1               .00000   -1.06675    -1.06675    -1.06675    1   o1               1.84767    1.06675     1.06675     1.06675    1   o1               1.84767     .00000    -2.13350     2.13350    2   cu1              3.01722 SPECS: Demeter 0.9.26 (pre2) Win10x64 AMD64 -R.