[QE-users] Symmetry Considerations

Offermans Willem willem.offermans at vito.be
Thu Jan 10 16:29:45 CET 2019

Dear Quantum Espresso friends,

All my systems of interest have S2-symmetry, i.e. there is an inversion centre present.
In one of my previous mails, I complained about loosing symmetry. I calculate my systems
sequently with increased accuracy. I clearly started with a system with an inversion centre.

There was a message in the output of the first calculation:

     2 Sym. Ops., with inversion, found ( 1 have fractional translation)

I realise now that I did not read this message carefully. I missed the last part about fractional translation.
What does it mean?

At some point in the sequence of calculations, the output contained the following message about symmetry:

    No symmetry found

I was surprised about the lost of symmetry. Is it related to the fractional translation?

Today I put a lot of effort to impose the symmetry. I read one part of the system from output and generated
the other part by inversion.

Now the output contained the following message:

    No symmetry found
          (note:  1 additional sym.ops. were found but ignored
           their fractional translations are incommensurate with FFT grid)

How can I bring the fractional translations of the sym.ops in commensurate mode with FFT grid?

Met vriendelijke groeten,
Mit freundlichen Grüßen,
With kind regards,

Willem Offermans
Researcher Electrocatalysis SCT
VITO NV | Boeretang 200 | 2400 Mol
Phone:+32(0)14335263 Mobile:+32(0)492182073

Willem.Offermans at Vito.be<mailto:Willem.Offermans at Vito.be>

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