[QE-users] Error in scf calculation of large number of atoms

[Pooja Vyas]

Dear users,
I have an input script (scf1.in attached below) of CaO with 2 atoms. It
runs fine for scf calculation.
I want to compute the energy of CaO with 64 atoms. So I opened scf1.in file
in XCrysden so it displayed 27 atoms and then I followed the below steps:
1) Display->Unit of repetition -> translational asymmetric unit
2) Above step reduced 27 atoms to 4 Ca and 4 O atoms totalling 8.
3) Then I followed Modify->number of units drawn and selected 2,2,2 in it.
So, it displayed 8 atoms*(2*2*2)= 64 atoms.

I took these atomic positions and made the file scf2.in attached below. But
on running that script for scf calculation, it shows me the following error:

 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     task #         1
     from check_atoms : error #         1
     atoms #   1 and #   2 differ by lattice vector (-1, 1, 0) in crystal
axis
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

The error is due to overlapping of atoms. But can anyone let me know how I
can compute the energy of 64 atoms? How do I figure out the equivalent
atomic positions which causes this error?
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