The ABINIT Users Mailing List ( CLOSED )

[Vadim Torchinov <torchinov@yahoo.com>]

Dear Gian-Marco,
thank you very much for last message. It was really helpful.

One more question: why does the presence of non-symmorphic operations
in the symmetries list cause problems? Does it cause wrong
wavefunctions in _STA (or _KSS) file to be produced?

Best wishes,
Vadim.


--- Gian-Marco Rignanese <rignanese@pcpm.ucl.ac.be> wrote:
> Dear All,
> 
> Some of you have recently reported a problem with the GW calculations
> in ABINIT. We have tracked the origin of this problem to the presence
> of non-symmorphic operations in the symmetries list after suppressing
> those related through the inversion symmetry. The possibility to deal
> with this kind of operations is not yet included in the GW part of 
> ABINIT (we hope that it will be in a "near" future).
> 
> So far, the program would just give a WARNING ("The GW program may
> give incorrect results"). Starting from ABINITv3.4.3, we have decided
> to replace this WARNING by an ERROR. Therefore, the program will not 
> produce the _KSS file when non-symmorphic operations in the
symmetries
> list after suppressing those related through the inversion symmetry.
> 
> What should be done to go further in such situations?
> 
> 1) In some simple cases, it is possible to choose the atomic
positions
> in such a way to get rid of the problem. For instance, in the case of
> 
> Silicon (2 atoms unit cell), one can choose either:
> xred       0.000  0.000  0.000          0.250  0.250  0.250
> or:
> xred     -0.125 -0.125 -0.125          0.125  0.125  0.125
> 
> In the first case, the GW calculation works perfectly; while in the 
> second one, the rotations (without inversion) are non-symmorphic.
> 
> 2) In the other cases, the symmetries list should be checked in 
> details. All the symmetries that are related through the inversion
are
> now (from ABINIT v3.4.3 on) indicated explicitly in the log file. The

> remaining operations that are non-symmorphic can thus be found
> easily. 
> Finally, the calculation should be restarted with the list of 
> symmetries that should be taken into account explicitly indicated in 
> the input file (use nsym, symrel and tnons).
> 
> Best regards,
> 
> Gian-Marco.
> 


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