[QE-developers] Incompatible FFT grid in ph.x calculation

[Paolo Giannozzi]

I see: it's the usual problem with "almost-symmetric" coordinates. If you
transform the "almost 1/3" and "almost 2/3" into something closer to 1/3
and 2/3 in the x and y atomic coordinates, the error disappears. In the
previous version of the code, the checks were done  in a slightly different
way and this problem did not show up.

Paolo

On Fri, Aug 14, 2020 at 3:22 PM Paolo Giannozzi <p.giannozzi at gmail.com>
wrote:

> On Fri, Aug 14, 2020 at 2:51 PM Xiao Zhang <xiaozha at umich.edu> wrote:
>
> I realized that in 6.6, an additional line shows: Fft bands division:
>> nmany = 1 (line 15). Not sure if this means anything or not?
>>
>
> it doesn't.
>
> Apparently the check on fractional translations being commensurate with
> the real-space grid is a little bit too strict. Not sure how to fix it in a
> safe way, though
>
> Paolo
>
>
>> Thanks!
>> Best!
>> Xiao
>>
>> On Fri, Aug 14, 2020 at 8:31 AM Paolo Giannozzi <p.giannozzi at gmail.com>
>> wrote:
>>
>>> It would be useful to see the scf output for v.6.5 as well
>>>
>>> Paolo
>>>
>>> On Fri, Aug 14, 2020 at 9:14 AM Xiao Zhang <xiaozha at umich.edu> wrote:
>>>
>>>> Dear QE developers,
>>>>
>>>> I'm sending the email asking about an error I get from the phonon
>>>> calculations in the 6.6 version of quantum espresso. I'm trying to run
>>>> phonon calculation for 2H SiC and have the scf run finished with no
>>>> problem, but when I run phonon calculation following that, I received an
>>>> incompatible FFT grid error. This happened only with the new version of QE
>>>> while using the exact same input, QE 6.5 works fine and provides output. I
>>>> was wondering if this is something we expect? (I do realize there is one
>>>> potentially relevant tag on the release note under "fixed")
>>>>
>>>> I attached one example just in case it might help: This is 2H-SiC and I
>>>> attached the input and output from scf, input and output from ph.x from
>>>> both 6.5 and 6.6. The k-points and cutoffs are reduced for quick tests, but
>>>> converged k-points and cutoffs show the same issue. The structure is
>>>> relaxed within QE, and the PP used is ONCV-PBE. I'm a bit confused why this
>>>> is seen in phonon calculation but not the scf calculation? I assumed that
>>>> if it's a problem of my input structure, I should've seen a problem in
>>>> both? Any hint or suggestions would be very helpful!
>>>>
>>>> Thanks a lot!
>>>> Best!
>>>> Xiao Zhang
>>>> Department of Materials Science and Engineering
>>>> University of Michigan, Ann Arbor
>>>>
>>>> _______________________________________________
>>>> developers mailing list
>>>> developers at lists.quantum-espresso.org
>>>> https://lists.quantum-espresso.org/mailman/listinfo/developers
>>>>
>>>
>>>
>>> --
>>> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
>>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
>>> Phone +39-0432-558216, fax +39-0432-558222
>>>
>>>
>
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>

-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/developers/attachments/20200814/bec6cf29/attachment.html>